user2306: In the transaction's version field, what values are legal?
What values have actually been seen in the blockchain?

user24925: 
In the transaction's version field, what values are legal?

The version field is a 32 bit unsigned integer, any value is valid. Version 0, or version numbers above the nodes CURRENT_VERSION constant are considered non-standard and are not relayed, though they can appear in blocks. 

What values have actually been seen in the blockchain?

1 is the only number to have been in use at this point in time. BIP62 proposes bumping the version to 3 (skipping 2 entirely) to match the block version and avoid confusion, however this was withdrawn. BIP68 specifies that transactions spending a CSV output must have version 2 or higher.

2306: <p>In the transaction's version field, what values are legal?</p>

<p>What values have actually been seen in the blockchain?</p>
 24925: <blockquote>
  <p>In the transaction's version field, what values are legal?</p>
</blockquote>

<p>The version field is a 32 bit unsigned integer, any value is valid. Version 0, or version numbers above the nodes <code>CURRENT_VERSION</code> constant <a href="https://github.com/bitcoin/bitcoin/blob/b94ae81576c199c9a44453b8c9b17e8303f67b72/src/policy/policy.cpp#L61-L64" rel="nofollow noreferrer">are considered non-standard and are not relayed</a>, though they can appear in blocks. </p>

<blockquote>
  <p>What values have actually been seen in the blockchain?</p>
</blockquote>

<p><code>1</code> is the only number to have been in use at this point in time. <a href="https://github.com/bitcoin/bips/blob/master/bip-0062.mediawiki" rel="nofollow noreferrer">BIP62</a> proposes bumping the version to <code>3</code> (skipping <code>2</code> entirely) to match the block version and avoid confusion, however this was withdrawn. BIP68 specifies that transactions spending a CSV output must have version <code>2</code> or higher.</p>
