'Classic' ie 50-60's ones fit, I know as i've fitted one to my thruxton (after i polished the cases as the lacquer finish failed.) Vintage meaning pre 1931 in the uk biking world no idea if they fit - but hey coventry triumphs are the true triumph!!!
Local auto shop sold me double sided car badge tape that holds it on, i bought the 'correct' rivets cut the heads off and glued them on. Looks good, would look even better if i'd managed not to put it on wonky!!! would post pic but currently don't have one to hand and the bike is in storage as i'm working overseas (with no bike!!!!) - but yes they fit.
The Meriden patent badges fit fine. If you want to use the original twist rivets, remove the cover, drilled three tiny holes, put a dab of clear silicon on each of the holes and then use the twist rivets to attach the plate. Clean around the holes on the inside of the cover and put a dab of silicone there too. Mine has been on there for over two years, still looks good and no oil weep.
Also worth noting, if you clean the plate too often the print will eventually be rubbed off and you'll be left with a gold or silver plate depending which one you fitted.
t'other cool old school thing to add after your patent badge is the 'worlds fastest motercycle' decal as fitted to 60's bonnies. http://www.domiracer.com/decals_triumph.html
scroll down there and you'll see it fits on the tank t'other side of filler cap - also fitted to my bike. this transfer and patent badge (with rivets) i got from fleabay.
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