Hi Kurtl
I suggest you look for a part number or extrusion number as that is your best key
For example 75- would indicate P-40 or B-17 or PT-13/17 or A-35 as a start. The Ham Std prop rules out the P-40 and prop size the PT-13/17. The B-17 and A-35 can be identified by the way the rest of the part number is structured
North American and Bell also use a 2 digit prefix followed by dashes tho NAA (like Douglas) like to use the same part as often a possible - eg BT-9, BT-14, Yale family/BC-1, AT-6, T-6 Harvard family/ A-36 and P51 family, B-25 family and 0-47 family all use the 19-53054 seat bracket in some or all versions
Convair use two digits followed by a letter (28 for Catalina and 32 for B-24)
Seven digits straight (with no prefix and maybe a -suffix) is most likely Douglas or Northrop and are somewhat harder to suss out as a C-47 part can be just one digit different from an A-20 part
A prefix letter followed by a - and six (from memory) digits indicates probably a Martin aircraft
There appear to be inspection stamps on the part. These also can identify the manufacturer tho being an extrusion they may be Alcoa stamps for production and heat treat
An elongated D with numbers inside was one of the Douglas stamps.
The caution here is that some manufacturers made parts for others and a lot of stuff was made by others - eg NAA made parts for Curtiss and Ford built most B-24s
Finally in the second bottom photo those may be cable supports on a part that has loosened OR anti-rotation lock tabs (the curved over part prevents the whole bolt rotating an both are in the location you should find them - ie the ccw edge firmly against structure)