Assuming all of that is absolutely required,
consider the following:
I have 8 rimfire shoulder arms in my safe that were
manufactured prior to GC68,,
none have serial numbers,,
all were purchased after Jan. 2001 from FFLs.
If I try to sell any of these firearms today to a FFL,
or take them for an evaluation, how screwed am I?
It is my understanding that you would be OK on those with no SN.
If it is reasonable to anyone that they were mfg prior to 1968.