Hi paul,
Regarding your 2 3/4 bits you mention, I think Paul is in the right ball park but it could be an earlier frame, the gearbox notation suggests that it should be a clutch type, The frame number suggests it could be earlier possibly even 1916-19. You do not mention an engine, if you have that the engine number would be a great help, the number is usually stamped on the case at the bottom of the rear cylinder. If its possible to post a couple of photo's that would help too. I can only give you info as an ex registrar working from our data bases, sadly I have never got involved with all the variations of that era of 2 3/4's.
However we do have members here in the UK ,not too mention all the owners in Aus! that may be able to give you more detailed identification. If you can manage photo's I will bring them to the attention of these members, not all of whom are into computers!!!
Is there sufficient for you to rebuild the bike?
cheers Dave.