It is a 20 " 1870 g ride , has a 6-number seial starting with 3, below or above the serial(below the bell) is nothing, so I think it's from 1973. But except for the stamp (in the 3 o'clock position) there is nothig more signatures. pictures:

http://href.hu/x/46np
http://href.hu/x/46nq
http://kepfeltoltes.hu/071216/IM000259_www.kepfeltoltes.hu_.jpg

http://kepfeltoltes.hu/071216/IM000254_www.kepfeltoltes.hu_.jpg

If there's a stamp a 3 o' clock, it's an original Giant Beat.

I asked Paiste, and they also said it's a GB from 1973.
How much can it worth, then?