The model and serial number seem to indicate this is one of the last of this particular style. The serial number, I believe, dates this machine to 1956.
Hmmmm.... 1956 seems to be a popular year in my collection!
The original unicouple faucet connector is pretty cool. Reminds me of the upper bowl of a Sunbeam vacuum coffeemaker! The hoses seem to be in good shape still. That plug's gotta go, though...
And the test was a success! I let the machine complete a 'dry' cycle and it did just fine.
I am still fearful of a cold snap, so I put off a water test for now. But it will be happening soon, I hope!
That's really fun - love the red dial! Congrats on another cool find. I'm sure you'll find that impeller out there somewhere, it's worth the hunt for that cutie.
Paul, That is a great looking Mobile Maid. Did the lid open on it's own at the end of the cycle? My 1SP40M1 does. Your serial number: 56300527 (56=1956, 30=30th week - week of July 22-28).