Anyway, the board is in very good condition and after I gave it a good bath, I could check those BTC dome with slider switches, I heard so much about. And I must say Chyros was right: they are very good, for a rubber dome solution. Very tactile and snappy, not too mushy and you don't have to bottom out to register a keystroke. Although, with such a strong tactile bump, you can't really avoid it.
If anyone is interested, here is a picture and some specifications from the User's Guide:

Production date: June 1997
Total travel: 3.5+/-0.5 mm
Pretravel: 1.0+/-0.5 mm
Operating Life: 20 million cycles
Tactile force: 60+/-20 g