Not sure if the F is the same as the K model, but the older K models had a number stamped into the tumbler cover. A honda dealer could supply keys if they had that number. I read somewhere once that bikes when new, were supplied with 3 keys. Two for the owner and one for the dealer to keep. Some shops had a big jar full of keys, and could supply keys because there was a relatively small number of ignition tumblers made for all Hondas of the period. I bought keys for my K5 a few years ago, (fairly recently). They were proud of 'em
tho, at 10.00 each...Hope your F model is similar in that regard, and assume the seat takes the same as the ignition lock..Good luck with it.