This is a very late model, evidenced by the 'F' prefix. As I understand it, the 'F' prefix began in Jan/Feb 1975 and continued until late Dec 1975. However, for some reason (according to Thrale I believe - see his book on Webley air rifles and air pistols), the production numbers suddenly jumped from around 1500 to 4500, with nothing in between. It sounds as if yours was one of the very last made, perhaps in Dec 1975, but others here will be able to furnish precise information. I recall production finished some distance before F7000 was reached.

Pity it has lost the disc.

Has it been knocked about?

Any idea what it is doing over the chrono?

Rgds
A