When you say "backs", do you mean what would be the "inside" of the cymbals, when they are on the stand? That side didn't have blue labels on them, at least for the Hi-Hats. (The Bell and Heavy Bell cymbals didn't have blue label on the bottom side either. I don't know about the splash)

Formula 602's from the 1980's would have had blue ink logos. If yours doesn't have any, more than likely they've been cleaned off.

Hey guys.. Thanks for the responses.. I have the logos and mint visible ink where they're supposed to be, i just meant underneath the bells.. But i did look over some pics on the internet and it seems they never had any ink there.. I find it strange since my vintage 2000 mediums have the ink both on tops and underneath both cymbals.. I guess it's some sort of anomaly ..

Hats are often different because in normal use nobody sees the inside of the hats. Thus there isn't any point in putting a big ink logo there. Not so with other types of cymbals where the underside can be seen by the audience.

I don't have a definitive list of which brands put big logo ink inside hats and which don't, but this pattern is true on must of the ones I've seen. A Zildjian (specifically checked New Beats as part of another project)? No. Sabian -- looks like they have the model on one of the hats (the bottom hat -- where the inside would face up during use) but not the big Sabian logo. Ufip? Nada. Paiste? They seem to follow the Sabian style for some lines and just put Paiste on the inside of the bottom hat (which will face up in use). Although I just looked at some reissue Giant Beats and they have a relatively small Paiste on both of them. So Paiste seem to mix it up in terms of their strategy. I haven't gone and looked at others, but I think you get the general idea: don't bother to put big ink logos where nobody will see them.

Asaik, there are no markings on the inside of hats from that era of 602's, except for the Sound Edges, which have the patent information on the inside of the bottom hat.