Every Bomar hatch has a coded number on it. That way they can ensure any replacement will match the original. The number acts as a serial number and states the hatch date of manufacture etc.
You will need that number so they can match correctly for you.
Each hatch produced by Bomar has a unique number on it so they can match a current product to the original. It's been that way for many moons.
I will not question you on this but seems real odd and costly that each unit is that unique. Normally a model number would have tolerance built into it.