'75 seems a bit late, but I'm just going by the fact that my first "pro grade" drum set was Pearl Fiberglass, purchased in '76. The lugs were the "newer" shaped lugs, and a cursory look over to the "reference books and catalogs" section under Pearl I found this 1975 catalog cover:
[IMG]http://www.vintagedrumguide.com/images/my_collection/catalogs/pearl_catalog_1975_cover.jpg[/IMG]
The difference in quality at that time and the snare drum you have (which is an amazing looking drum, by the way!) is fairly pronounced. They had a new throwoff mechanism that was a die cast that had a lever on top, and it flipped down to de-activate. Overall, in '75, at least, Pearl had arrived in the Pro-quality era of drums to stay.