It turned out to be a featherweight card table:
And my featherweight footed the gap perfectly! What a stroke of luck! This is why I love thrift shopping, because once in a blue moon you find a miracle bargain.For some reason blogger is glitchy this week when I try to paste links so I can't post an active hyperlink for Singer cabinet and table info but here's the web address you can copy and paste into your browser if you want to learn more about these tables:
https://ismacs.net/singer_sewing_machine_company/singer_sewing_machine_cabinets.html