Q:

Meaning of remarks on 1948 USMC discharge papers?

I am trying to understand the full meaning of the remarks shown on this record from the United States Marine Corps (USMC) Muster Rolls. This is from July, 1948.
(column headers)

(record in question)

The numbers in the first (NO.) column refer to records within a rank. FEITLER was in the "Corporals" list. 
I am interested in the meaning of footnote "K"; I believe 30 is the man's age. 
Does sat ser mean satisfactory service? 
Where can I find "SPEC NO" code meanings?

A:

The image is actually from a set of muster rolls, for which one part of this batch of returns is subtitled, "Discharged." The graphic below is from the same image page listed above, it shows the subheading. (Your man FEITLER was the fourth listed corporal.)

See Ancestry's "Source Description" for "About U.S. Marine Corps Muster Rolls, 1798-1958." Citing James C. Neagles, U.S. Military Records: A Guide to Federal and State Sources, (Provo, UT, USA: Ancestry, 1994)

Muster rolls are lists ... of the names of soldiers assigned to any military unit ... The rolls were made at the time a unit was created (muster-in rolls), when a unit was reorganized, when two or more units were merged, and when a unit was disbanded (muster-out rolls). Names appearing on a muster roll indicate those who were present or accounted for on a given date ...This roll was used as the basis for pay due the soldiers ... Remarks might include information about any individuals absent or deceased ...

I suspect there are separate discharge papers about your marine. 
Sadly, it would seem US Marine Corps officials have chosen to move relevant personnel manuals off-line. See, for example, "Marine Corps Personnel Manual (MCPM) (1949)." Note the foia ("Freedom of Information Act") in the URL; then click the link for the big "404  - Page not found." Links like "United States Marine Corps (USMC) Orders and Directives," "USMC Chronologies," and "USMC in WWII" on the "USMC FOIA Reading Room" also returned 404 errors for me. 
While the Marines likely had different procedures, the discharge papers in my father's US Army 201 file are quite different than these "muster rolls." Dad was actually honorably discharged twice; the back side of each "discharge" paper includes a summary of service.  
Blush, blush, blush. I just realized that in my personal files I have the final discharge papers of two men--my father (1946) and his ancestor, Rev. War patriot, William Preston (1780). Wow. What an honor. 
You inquired about "Footnote K"; it can be found in the same batch of images. The image you reference is actually 626; there are footnotes that seem relative to that batch on 629 of 995. 

(I was working on a better graphic, may yet pop it up here.)
You inquired about "Spec No"; it is likely aka Specialist Number, which would identify a functional position/job. See "Marine Corps Officer Job Descriptions" (About.com), "Marine Corps unrestricted line officer, limited duty officer, and warrant officer jobs have specific designators, called "Military Occupational Specialties," or MOS. Similar MOS's are grouped together into occupational fields.". This article goes on to list/link to present day Marine Corp "Office Jobs." 
While the classifications likely changed, for time relevant usage of the term "specialist number," see the article, "Marine is one of 26 from  company to survive Iwo Jima" (Sauk Valley Media, November 14, 2011) 

Oliver Taylor stormed Japan’s Iwo Jima with 284 Marines at his side.
  With barely a scratch, the machine gunner sailed back to Hawaii’s
  Pearl Harbor with just 25 men, only to be redeployed for a planned
  invasion of Japan ... “I was an especially big target, because everyone wants to lick a machine gun man,” Taylor said. “I got that specialist number, and I
  couldn’t get rid of it.”

Only somewhat related, in my dad's Army 201 file, the document that served as the authority for his final discharge was called a "Separate Qualification Record," it contains his "Army Serial No" and a list of his assignments, each of which is associated with a "Military Occupational Specialty" that was identified by a title such as "Supply and Evacuation Officer Staff" and a number, like "2100."
You inquired about "sat ser." The reference "U.S. Navy Abbreviations of World War II" didn't include the combined abbreviation. According to that reference "Sat" means "saturated"; in this context, "Ser" would mean "service." (Perhaps someone will find a reference to the combined abbreviation.) 

Additional references:
"U.S. Navy Abbreviations of World War II," by asisbiz (asisbiz.com), reportedly  "The text of the [Glossary of U.S. Naval Abbreviations which] was prepared shortly after the close of World War II. Transcriber/site owner reports it is "exactly as in the original, except that fifty-nine words which originally appeared in an addenda page have been integrated in the main text of the document." [Wow!]
Julius Augustus Furer, Rear Admiral, USN, Administration of the Navy Department in World War II (1959); electronic typescript version, The Public Library and Digital Archive. Includes the chapter"The United States Marine Corp." 
Division of Public Inquiries, Office of War Information, "Department of the Navy," United States Government Manual, 1945; electronic typescript version, The Public Library and Digital Archive.
Patrick Clancy (deceased), "HyperWar: A HyperText history of the Second World War, especially for Links and additional resources, "US Marine Corps in World War II." 
According to the Ancestry.com description, the database and digital images that make up, "U.S. Marine Corps Muster Rolls, 1798-1958," come from two National Archives (NARA) collections:

Muster Rolls of the U.S. Marine Corps, 1798-1892; (National Archives Microfilm Publication T1118, 123 rolls); Records of the U.S. Marine Corps, Record Group 127; National Archives, Washington, D.C. 
U.S. Marine Corps Muster Rolls, 1893-1958; (National Archives Microfilm Publication T977, 460 rolls); Records of the U.S. Marine Corps, Record Group 127; National Archives, Washington, D.C.

See also, Trevor K. Plante, "An Overview of the Records at the National Archives Relating to Military Service" (Prologue: Selected Articles).

A:

This image is from the unit muster for whichever unit he was in at the time.  It is a chronological record of who was in the unit at the time.  
The muster is created when the unit is formed and then updated monthly with any unit activity such as personnel joining, transferring, discharging, etc.  In this case it is for the month of July, 1948.  
The 4 in the No column indicates he is the 4th Corporal listed in the chronological record of discharges section.  The Serial No column is his service number (used before the SSN was used as the service number, since replaced by the EDIPI).  The Spec No column indicates his specialty (now military occupational specialty or MOS).  Specialty 745 indicates he was a rifleman (now called an 0311 or grunt).  The Remarks column is a record of what happened to this individual during this month.  The See footnote "K" means there are other remarks summarized in a footnote that was too much for the remarks section or (more likely) applied to more than one person on the muster. 
If the other pictures posted are from the same record, footnote K would indicate that on the 25th of the indicated month (25), he joined from (Jdfr)  his previous unit which looks like Marine Barracks (MB), 15th (15) Naval District (ND) Balboa C. Z. (Balboa Canal Zone in the Panama Canal).  He embarked on the the Naval Ship USS President Hayes on 18 Jul 1948 which sailed on 19 Jul 1948.  He arrived and disembarked at Naval Base (NB) Norfolk, Virginia on 25 Jul 1948.  
On 30 Jul 1948 (30) he was promoted (pro) to rank (in this case Corporal since he is in the Corporal section of the muster) from (fr) 30 Jul 1948 which means his date of rank for Corporal is 30 Jul 1948.  Also on 30 Jul 1948 (30) he was given a Convenience of the Government (CofG) Honorable Discharge (HonDis).  This was awarded (awd) certifying (cer) satisfactory (sat) service (ser), which was authorized (auth) by a Commandant of the Marine Corps (CMC) letter (ltr) to all Commanding Officers (CO's) dated (dtd) 11 Jun 1918.
Feitler gave them his home address (HA) as 7914 Saint (St) Lawrence Ave, Chicage, Illinois.  He had chosen not to reenlist (Will not reenl).  
Although I cannot find a record of the actual letter, the CMC letter to all COs date 11 Jun 1948 was likely a letter from the Commandant telling all Commanding Officers that they could, at their discretion, let Marines out of the Corps earlier than their contract would allow.  This is done fairly often in order to meet some objective or for some other reason.  They used to do this every year before Christmas if Marines were getting out early in the new year in order to allow them to go home for Christmas and not come back.  It is likely that this letter was allowing COs to release Marines early to assist with the post WWII drawdown.  
The letter also probably contained the authority to promote those that were eligible for promotion prior to their original contract expiring on their new discharge date so they didn't feel like they would lose out on a promotion if they took advantage of the opportunity to get out early.

