UPDATE:
So as Paul Harvey says, here is the rest of the story!
Keep in mind that I know zero about mini 14s up until this foray happened and I still really don't, but learning little by little. We ran the serial number, it did not come with a factory folding stock.
However the mini 14 was supposed to be original according to the owner, we'll now call him Senior. Then one day his son was home (Junior) and the discussion came to this mini 14 to which all the info was shared...Senior still disagreeing with Ruger, of course...when Junior pops up and says that Senior is mistaken.
Really long story...the condensed version is this...between Senior and Junior there are a number of mini14s hiding in the nether regions of the house. Junior at some point in the past wanted a scoped version in the folding stock, so he swapped two of them. So he rummaged around and found the correct mini 14 which does in fact have the side sling mount and matching serial number. Simple...problem solved. Well, that one anyway.
My problem now is that my trade deal has gotten complicated because he wants me to throw in more stuff from my end and take both the folder and the non-folder....
The original folder action looks to be in the same condition but does not have a scope mount or scope, but it was drilled for one...a single hole in the top of the action just in front of the rear sight. Shame, but what can you do. Easily fixed with a cut, peened and polished stainless screw, but that would be up to the next owner.
I am still standing on my original deal to take the folder only first and if that works out to sell in the range we need to make this work, then I will discuss the non-folder with him.
So I guess there really is no problem other than to throw it up on the EE and see what comes of it.
Thanks again to everyone for your help
