How to read letter/number combinations (location data?) on seeds?

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I'm not really sure what to search for to find this out.

Basically on more serious cacti seed sale posts online the species name is sometimes followed by a combinations of letters and numbers. I'm reasonably sure this is location data for where the seeds/mother plant was natively found. Presumably this is so collectors can verify the seeds are "pure" from a certain location i.e. not a mixture from different ends of a plant's geographical range, and so regional variations can be identified and collected.

I know nothing about the system though. Is there a registry somewhere or are the numbers/letter just allocated by the person collecting the seeds? Is there an actual system here?

I was hoping someone could point me the right way.

[esp_imaging]

I know of 2 databases. They are both incomplete, collectors do not always provide their information, and the databases need to be updated by their owners.

https://www.fieldnos.bcss.org.uk/
http://cl-cactus.com/