You do not say whether you have a 2 Speed or a Flying Squirrel/TT Rep frame. In both case the Frame No is on the headstock lug.
On the 2 Speed it is on the top surface of the side car mounting boss on the headstock.
On the FS/TT Rep frames it is on the nearside of the headstock lug. It can get filled in by paint. It is also not unknown for it to be defaced, restamped or removed to hide a change of frame.
