Tracking overall sales of parts from a laptop

[jweiss128]

Say I bought 10 laptops and I am taking them apart and selling the parts individually. I want to keep track of the overall sales of parts per laptop. How can I set up my listings to do this to see which laptop was most profitable? 

I know about the custom SKU field, but this doesn't seem like the right way to go about it.

[hartungcards]

Use the custom SKU field.  It's the right way to go about it.

[harborauction]

I'm an old timer so I sometimes still use pen & paper, if I had 10 different lots I wanted to monitor I would just put  a different inventory number for each lot in the listing descriptions then when one sold I would know which lot it came from

[jweiss128]

Do you know if I can add this after an item is sold?