The photo in the eBay listing is reversed (note the Singer lettering - it's backwards). I would also say that eBay seller is a hopeless optimist; that machine might be worth $35, but not $350. A quick Google search suggests that the 615U has all metal innards, and can do a chain stitch, but otherwise it seems pretty unexceptional.
Does anyone else know anything about this model? I read that the U was for machines sold through military depots only. If anyone can confirm/deny this, I'd be interested to hear about it.