Looks like a pretty clear shadow of a 4 to me. Oddly, I just got what I think is a similarly-faint 24-S in a batch of "dateless" SLQs yesterday.
eBay, of course. Oddly enough, although dateless SLQs are usually worn enough to be 5-10% underweight, they usually still trade a bit above "junk silver" face-value-multiplier rates.