I would do some free motion test stitching on both of them and see if they are any good. A 15 doesn't have the best satin stitching if at all, but the 306 might. There are some zigzager attachment that might do the basic jobs. The 306 looks almost brand new in the pictures, clean and shiny, it even has the beige pedal. The green machines I've seen usually come in pale wood cases or cabinets, but the teak table you have is very common on 1950s machines in general. I have a 201K23 in what looks like exactly the same table, but it's not as dark as yours. Mine is a bit sun-faded I think, but probably a shade or two ligter originally. The color is better preserved in some areas than others.
Last edited by Mickey2; 08-21-2017 at 06:41 AM.