What i have been told from 1 of the Winder here is that the vintage magnets are a different measurement than todays magnets . So that might be 1 way to help you know what you have. Or at least a start .
I quote "Vintage Guitars Info's
Gibson PAF (Patent Applied For) Humbucker Pickup Info.
From 1956 until 1961 Gibson used different Alnico magnets in their PAF pickups. Alnico magnets (alloys ALuminum, NIckel, and CObalt) come in a different grades based on their magnetic strength. Gibson generally used the same magnets (size/grade) which was available for their P-90 pickups. But Gibson randomly used Alnico 2,3,4,5 grade magnets in PAFs until 1961 (remember the higher the magnet's number, the higher the magnetic strength). This can often account for how two PAF pickups can sound quite different. In July 1961 Gibson began consistently using a smaller Alnico 5 magnet (smaller as in the flat top side of the magnets were smaller length-wise). Since inconsistency was king at Gibson during this time, Alnico 2 short magnets are sometimes seen too. By 1965 though Alnico 5 was the standard for all Gibson humbuckers.
The original PAF magnet length was 2.5" long, which was decreased by 1/8" to 1/4" to around 2.25" in July 1961. But the "short magnet" PAF can be seen as early as 1959 and is still original. Gold plated guitars (ES-345, LP Custom, etc) seem to use the short magnet PAFs before nickel plated guitars (like the ES-335, LP Standard, etc). Just from a consistency point of view, July 1961 is the date considered by most as when short magnets were the norm for PAFs. Generally speaking decreasing the length decreases the power of the pickups, but this was somewhat counteracted by the Alnico 5's added strength. When new, the shorter A5 magnet is more powerful than the longer A2 magnet. So do short magnet PAFs sound worst than 1957-1960 long magnet PAFs? NO. In fact, they may sound better in many cases. But there are lots of things that effect sound, with the magnet only being one piece of the equation.
Dimensions of PAF magnets follow (measured using a micrometer, and obviously this will vary a bit from magnet to magnet): 2.509" long ("long magnet" version), .506" wide, .131" thick. The "short magnet" PAF length was the a bit different: 2.371" long, .491" wide, and .121" thick.
Gibson PAF Humbuckers Pickups Patent Applied For Pickups M69 M-69 pickup rings - Vintage Guitars Info
good site for info on PAF's
BTW- I was the 1 who bought the PAF short magnets from HM . very nice