Sorry guys...I've been in Europe for a couple of weeks and couldn't respond. Here's what I know...
Formula 602's originally came with only the stamped shooting star/formula 602 and no serial numbers. These cymbals were produced from 1959 to late in the 60's although the end date is unclear. In the mid-60's some the pre-serial cymbals began to also include ink stamps with the size (ie: 18") and type (ie: medium). The labels were usually on the underside of the bell.
In the late 60's through the late-mid 70's Paiste began to add serial numbers to these cymbals as well as black labels. This was known as the black label era. The labeling is in the form of a relatively simple script which says Paiste Formula 602. Size and type were also labeled at 90 degrees clockwise in the same printing direction. Paiste also continued to stamp these cymbals as before.
In the 80's, Paiste went to blue labels which mimic the shooting star stamp. Size and type were labeled as per the black label era. The blue label era were the last form of the Formula 602 cymbals until they were discontinued in 1987.
Formula 602 cymbals are remarkably similar regardless of era and were manufactured with the same methods throughout the series lifetime. This is a testament to the Paiste manufacturing system which produces each and every cymbal to match a master cymbal in sound. Of course, there are collectors who prefer various eras and feel that there are minor sound differences between them but in the end I think its just preference for the look of the cymbal. I have tried cymbals of each era and there is virtually no difference in sound quality. This is great news for collectors because it means that as long as the cymbal is intact and not damaged it is pretty much guaranteed to sound great. My pre-serial collection is a testament to this....not a bad one in the bunch.
Regarding Ludwig/Paiste cymbals, as the result of a marketing agreement these were produced during the 60's for sale with Ludwig drum kits. There are at least two versions the most common of which are:
Ludwig Paiste (3 stars) - These cymbals were made from the same B20 alloy as the Formula 602's in Switzerland. They tend to be thinner cymbals so you must be very careful when looking at purchasing used ones. Thinner cymbals tend to be more susceptible to damage and even small dents and warpage can negatively affect the sound of these cymbals. Condition is everything. Rides tend to be more common in Jazz sizes. Hats are also common. Crashes in good condition are rare.
Ludwig Standard (shooting star) - These cymbals were made from the B20 or the NS12 alloy. NS12 will be more silvery in color and will typically have the "German Made" stamp although this is not 100% true since some of the larger sizes were made in Switzerland also. NS12 cymbals can be great shimmery sounding pies with less dark overtones than B20, but the alloy is soft and the cymbals are easily damaged therefore you absolutely must play and listen to the cymbal before purchasing. I can attest to this as I have a few dogs around. These cymbals may also carry the "Swiss Made" stamp and are usually B20 cymbals if stamped in this way. These cymbals also tend to be thinner than Formula 602's. The same comments apply as for the Ludwig Paiste cymbals re: condition. These cymbals also tend to be more common on the market.
