I can't quite make out your serial number but it looks like it starts with a C. Mine is C47xx (1993) and the 16 round MecGars from Greg Cote work fine.
I think that 93 is when the magwell opened enough to allow for modern mags.
I have a 92 (75, not 85), and it's too tight for them. Mine has the round trigger guard.
Of note, I bought a 3 pack of the SP-01 mags (either 18 or 19 rd) from CZ, and those do fit and work perfectly. They hang out the bottom, but come with a spacer that fits flush. Not really a spacer, but the base extends up the mag. The base rides flush. It looks a lot like an 8 rd mag in a 1911.
I bought the 3 pack when it was on sale for about $100, they usually run that deal fairly often.
Added- I bought another 75 for my son, so he won't steal mine. It is an 89. The SP01 mags also fit his
I HATE to recommend the following, but just to be fair:
the CZ USA website now lists 16 rd mags for the Pre B 75/85, although they are a little steep ($43 apiece). They have a rubber base, not the metal base the old ones have.
Added- not really sure what the material is, actually, it looks rubber or plastic. Basically, it most closely resembles the base on a newer Beretta mag, or for a 3rd gen S&W; there is some extension, instead of the flat piece of metal that would seat flush like the old CZ mags do.
I did a google search to see if anyone else has them, and I did find another place, for less: Cheaper Than Dirt. They have the identical mag, specified for pre B, for $32.29.
I, like many, despise what CTD did during the ammo shortage, but it might still be the best price you can find. Before you swear that they will rob you with shipping: just for fun (and to check the price for this thread), I logged in, placed 2 in my cart, and started the checkout so I could estimate shipping.
It came back with $6 s/h using UPS SurePost 7-10 day.
In other words, 2 new 16 rd mags for $70 total.
Final edit: the product code is the same for the CTD and CZ USA mags, it is the same mag.