To help in determining what lock mechanism you are asking about:
The pictures below are to help identify keys some times the keys maybe a different size for example: Pin tumbler key for some padlocks are under 2 inch length
All pictured versions were purchased in North America. Here is a list of where it is common to find each lock mechanism and key type:
Here are examples of places to look on a lock to help identify the lock
In the red boxes Left to Right Picture 1 Manufacturers name on front, Picture 2 other identifying marks example:(markings,holes,cross,codes,logos), Picture 3 Manufacturers name on latch if not on front or hard to read on front
Example of code found on cabinet locks is in red box:
Besides the code if you have information about these things it will be a lot easier for a locksmith to determine if they would be able to handle the job: