The 66 serial number is in the group that was allocated May 1931. If the cabinet is in good condition and you have the stool, you could ask $50, without the stool, then $25 - $30. I'd say $25 for the second one. IMO - neither fall in the range of "collectable" though the Singer is in very nice condition. Or you could ask $100 and hope someone is willing to purchase because it's going for a good cause. I've been known to pay over what I know is market for something that a charity was selling.
Now - if you happen to have got some of the less common attachments with the Singer - then you could be talking some serious money sold on eBay.
A word of warning about looking on Craigslist - it's more likely to shows you what they ARE NOT selling for. Those priced to sell get sold and deleted (usually, unless the seller is lazy about it) those still listed are usually priced over market - especially if they have been there several weeks.