The owner told me they're vintage - probably 1920s-30s, but I can't really remember the details - and I can't find anything online either! It's really frustrating...
If anyone recognises these, and what game they are for, do let me know! I think it's a form of Snap or Old Maid, but without a box or instructions, who knows?
In any case, I've put them up for sale on eBay as I'm still frantically de-stashing. I've got around 8 sets of vintage cards in all - Heaven knows what I was intending to do with them all!
Meantime, you're welcome to download these for Personal Use, if you'd like to use them in scrapbooking and projects. Just click on the pix to bring them up to full size, then right-click to copy them. They're totally unretouched, and scanned at a large size.