Sorry about your dilemma. I know nothing about Singer bobbins except they don't play well in my Kenmore or H/V. Is there a definite way that they fit into the machine. My drop in H/V has to have the H?V emblem up in the machine and on the bobbin winder. The Kenmore doesn't have a preference.
Once you figure out what you do have, could you put a small dot of red nail polish on the right ones so you could tell at a glance which are your soldiers and which ones need to be held in captivity for some other unsuspecting buyer (include a note of apology)?