The logic behind Omega part numbers

Hey gang,

I'm currently looking for an Omega crown for a Constellation, ref. 168.029:


(this picture is not from the actual watch, but the exact same model)

I found the gold plated version on ofrei (no luck on cousinsUK or eBay), part number is 069SX42529. Unfortunately, they don't have the steel one, and I was wondering if the part numbers follow a certain logic, e.g. steel is always the next number, in this case -42530. If that's not the case and somebody is able to help out with the actual number I'm looking for, I'd also be very grateful! But since I've had that exact case a couple of times already I was wondering if there's any sense in the system, even though I'm afraid the answer might simply be "no". 😁

Thanks a lot!

Steel is ST instead of SX

Perfect, thank you. That was almost too easy. 😀

As @tdn-dk pointed out above the ST is correct. So you are looking for 069ST42529