Thank you for info about the combination table.

I worked with an early Singer 12K table, figuring how the portable might line up with belt, and made discovery. The 28K base will only set on top, the iron stand would conflict if set in table flush. The table was fitted with a Fashion Mate 360, before purchase. Top was repaired, and fit in Singer 28, without cutting original wood. Veneer was then applied.

I also measured and compared the latch receiver shown, to the pop-out legs and it was a match! Now my plan is to replicate the 1" diameter receivers with 0.60" x 0.34" rectangular slot for leg receivers and make top from a spare treadle top. With only four large screws, top can be changed over on stand.