It has some age but is in good condition. The rubber is slightly perished but still serviceable. 

Overall diameter 3 1/4 (8.2 cm) and unpacked weight is 72 grams. It is made from metal with a perspex cover and rubber seal. There is a chink out of the perspex but it's half moon shaped and it may be for ease of removal.

This is genuine vintage and has some signs of use.

Please see photos.