I recently purchased a box of miscellaneous vintage drum hardware and included in the lot was a bag of 120 or so mounting screws. Based on the research I've done, I believe the screws to be Slingerlands. However, I'm wondering if there's any way to tell whether they were manufactured in the '60s, '70s or '80s? Did the company actually use different screw configurations during the different decades or were they the same? Any words of wisdom would be greatly appreciated. Thanks in advance for your time and your help!