BoJangles

I just bought a Singer 99K at an estate sale. It is in a "Style 73 Walnut" cabinet. The little machine looks great, has all the attachments, a light that still works, runs smooth, was owned by the mother of the people I bought it from. I have the orginial receipt dated December 12, 1956. The model number is EL 260583 and I paid $10 for the complete package. The lady that bought it originally paid $153.40. What is it worth? I am not going to sell the little thing, but I'd like to know what it is worth in the original cabinet?
Nancy