This could either be item-unique (mac/seriel/id or whatever) or as a whole, like "Radio, broken antenna" put into the service or warranty-department with status broken, in-repair or discarded or similar. The cost to put a separate expenseaccount.

And then perhaps an internal list of fixed/used item with a reduced price.
This list might not have to require login if only for diplaying or linking into another system (like sales-terminal for clerks in the store).

And the return of an assemblyd item (like a switch with two fibre-modules for example) you could ask you if you want to place the item as a whole, or dis-asembly the item into chassi + 2 fibre modules to the stock/assemblyinventory.
Marked as used ofcourse.

So basicly each item could have a duplicate "used" item to handle returnes or swapped items.

Regards
Rikard