I believe it should have the UL symbol on some sort of hollowgraphic sticker. However I shy away from anything the dollar stores carry though...how do you know the sticker is not faked!

If I have what looks to be lampcord in my wall and there are no visible markings, it may not even be UL approved lampcord. Right?

UL approval is not an issue.

Cord of *ANY* type is not allowed to be inside the wall PERIOD.
Doesn't matter if it's 12 volts or 1200 volts.

I looked at some 'lamp cord' that powers a string of flourescent undercounter lights that I have. There is a set of identification information embossed on the cable which is hard to see unless you get the light just right. One of the things embossed on the cable are the symbols (UL), which means that the cable is UL listed. IIRC, the identifiation information is usually place every 12" or so along cables of all types.

thank you, weedmeister. I don't see anything embossed on my lamp cord on the inches here and there that I can see.

Yep, it would be hard to see. White on White.