Model B fork, so probably a Model B. No holes in the lugs & older style seat binder bolt point to mid-late 1960s. The seat tube may have a decal saying "Model B" or "Special Corsa". The brakes are definitely a later addition. Check the top of the rear derailleur for a date. If none, just "Patent", derailleur may be original (68, 69). If you have the original wheels, check the lock nuts for dating. Pix of the seat tube decals, top & bottom of the bottom bracket & top of the rear derailleur would be nice.
The chrome isn't too bad- should clean up nicely.

Lucky you!

Also, a deeply cool Nitor seat post!