There is a simple convention to assign an ID to a VM:
IDs from 100 to 199 are assigned to masters VM
IDs from 200 to 299 are assigned to VM in production
IDs from 300 to 399 are assigned to VM in test (that may be in production in a near future)
IDs from 500 to 599 are assigned to VM that are not used or that were put out of production
IDs from 900 to 999 are assigned to VM created for experimental work