Every manufacturer uses its own part number convention. Reading them correctly is the fastest way to identify an aftermarket equivalent and avoid ordering the wrong component.
Canon
Canon hardware numbers follow a four character prefix plus a four digit suffix, for example FM4-8923-000. The final three digits usually indicate a revision, so FM4-8923-000 and FM4-8923-010 are often interchangeable.
Ricoh
Ricoh uses a letter and four digit pattern such as D149-2202. The prefix identifies the machine family rather than the part type.
Xerox
Xerox consumable numbers begin with 006R or 013R, for example 006R01697. Supplies and hardware parts are numbered in separate ranges.
Cross referencing
Search on the exact OEM number, then confirm the printer model and the physical appearance of the part. Where a number supersedes an older one, the supplier should be able to confirm both numbers refer to the same component.