Synchomesh on 2,3,4; none on 1st or reverse. Some TR3B got the later box with synchro on 1st (but still not reverse).
Sometimes the 2nd gear synchro is worn out as well, so it's not unusual to find one that acts like it only has synchro on 3 & 4. Possibly that's because people learn to use the 2nd gear synchro to stop the countershaft before shifting into 1st or revers.
Likewise, lots of folks retrofit the 4-synchro box into their TR3s (as I did). Not quite a drop-in, but an easy modification.
Good luck double clutching into 1st, I could never do it smoothly. Easier to start in 2nd gear if not a complete stop. 1st is also a lower ratio on the crash box than on the later 4 synchro boxes. If you need a stump pulled ...