A number of Sherman tanks were converted to carry different armament or fill different roles than those for which the tank was originally manufactured.
Among these were:
Tank AA, 20 mm Quad, Skink – Canadian prototype anti-aircraft vehicle with four 20 mm Polsten cannon mounted in a turret on a Grizzly hull (tank made in Canada, not Lend-Leased).

Sherman Duplex Drive (DD) – British-developed swimming gear fitted to British, Canadian, and US Shermans for the Normandy landings.

Sherman 17pdr aka "Firefly" – British Sherman I or V re-armed with QF 17 pounder (76.2 mm) anti-tank gun with C added to designation (as in Sherman IC or VC).
A few Sherman IIIC are believed to have existed, issued to units equipped with standard Sherman III for mechanical commonality: Aberdeen Proving Ground in the USA has one.
Post-war the "Firefly" name is commonly used to refer to these vehicles, but it was not an official name and not commonly used during the war.

Sherman Tulip – British Sherman with two 3-inch ("60lb") RP-3 rockets on rails added to the turret.
Used by the 1st Coldstream Guards at the Rhine in 1945.

RMASG "Control Tank" – Sherman V tanks allocated to the Royal Marines Armoured Support Group for the D-Day landings were fitted with a dial sight in a protruding square cover on the top right of the turret.
This permitted them to be used accurately in the indirect fire role as self-propelled artillery, initially from the decks of landing craft but later also ashore.
Direct fire sights were retained.
These tanks can be identified in photos by the 360-degree compass bearing markings around the turret.
A number of Sherman tanks were converted to carry different armament or fill different roles than those for which the tank was originally manufactured. Among these were:
Tank AA, 20 mm Quad, Skink – Canadian prototype anti-aircraft vehicle with four 20 mm Polsten cannon mounted in a turret on a Grizzly hull (tank made in Canada, not Lend-Leased).
Sherman Duplex Drive (DD) – British-developed swimming gear fitted to British, Canadian, and US Shermans for the Normandy landings.
Sherman 17pdr aka "Firefly" – British Sherman I or V re-armed with QF 17 pounder (76.2 mm) anti-tank gun with C added to designation (as in Sherman IC or VC). A few Sherman IIIC are believed to have existed, issued to units equipped with standard Sherman III for mechanical commonality: Aberdeen Proving Ground in the USA has one. Post-war the "Firefly" name is commonly used to refer to these vehicles, but it was not an official name and not commonly used during the war.
Sherman Tulip – British Sherman with two 3-inch ("60lb") RP-3 rockets on rails added to the turret. Used by the 1st Coldstream Guards at the Rhine in 1945.
RMASG "Control Tank" – Sherman V tanks allocated to the Royal Marines Armoured Support Group for the D-Day landings were fitted with a dial sight in a protruding square cover on the top right of the turret. This permitted them to be used accurately in the indirect fire role as self-propelled artillery, initially from the decks of landing craft but later also ashore. Direct fire sights were retained. These tanks can be identified in photos by the 360-degree compass bearing markings around the turret.
Lend-Lease Sherman tanks