Not quite sure what you are asking but there are some procedures to be followed (IF you are doing this officially) if a used part is salvaged from a scrap airframe.
On an N-reg the procedure is fairly well defined and basically a non structural part can be inspected by an A&P and declared as good. Only an FAA Part 145 Repair Station can generate a fresh 8130-3 for it, but you don't need an 8130-3 for the vast majority of parts. A structural part may require an A&P/IA and he may determine that it should be NDTd (which for a nose leg of unknown history is pretty obvious really).
On an EASA-reg plane, the practice varies. I recall asking one owner of an EASA 145 company how this works and he said that salvaging a part from another airframe is acceptable only if it has a valid CofA at the time (which a scrap aircraft obviously doesn't because the CofA is gone the instant the plane ceases to be airworthy). That was his take, which was I suspect a very strict one. In other circumstances, parts are being freely salvaged and I suspect often it is done off the logbooks. In some cases, the part is taken to an EASA-145 company which, for a substantial fee, "inspects" the part. In one case I know of, they "overhauled" it by changing one rivet (which didn't need changing). An EASA-145 company is capable of generating a fresh EASA-1 form and this is good enough for any installer no matter how anally retarded, but it is an expensive way around it. I've had obviously used parts sold to me by Socata, with an EASA-1 form, but Socata are an EASA-145 company so they can do anything.