welcome to the forum, Emily. Ajax, were as George says, made from nickel silver alloy and were an entry level cymbal. I have 2 of the 18" versions and one is lousy and the other surprisingly good. I keep them more for demonstration, than anything else. The lousy one is thinner and is covered in all kinds of dents and rimples along the edge----it already had them when I acquired it in 1967. The other one appears to have had it's share of use but is still dent free and the edge is straight.
These cymbals were cut and spun from sheet stock that was purchased from a jobber. My guess is that either the sheet stock was variable, possibly made with a lot of recycled material, or Boosey & Hawkes changed suppliers, because at some point, the cymbals changed in quality but their overall look didn't. If your cymbal is pretty much dent free, you might have one of the good ones( they sound a lot like a good K, with a nice dark wash, overlain by a solid precise ping., when played as a ride.). ......it's value? despite whether it sounds good or not, Ajax aren't anywhere near the top of anyones list, when it comes to cymbal acqusitions, so don't expect much more then 40 or 50 $ for it.