if they’re asking for a receipt for taxes then we have a cash reciept up on the wiki or on \files\ that one can print out and put the fare market value. (ie median price found on say ebay, round down.)
If one cannot find or use the prepared version then the basics anyone needs is for a donation is something like the following but with a DMS letterhead, details, etc…
Also, try to keep an inventory spreadsheet. A good example would be the one built for VCC:
Be sure to make a copy of the sheet for your own records.