Dull porcelain
Patrick -
Detergents back in the day sometimes used fine sand as a carrier to keep the detergent granular and not clumped. If you remove the basket I have a hunch there will be a decent layer of white build-up adhered to the bottom of the outer tub. This stuff was somewhat abrasive and over time could dull the porcelain. I saw that on more than a couple machines. I had one that was so bad that the top layer of porcelain was absolutely gone until you got about half way up the sides of the basket, then it reappeared. The lower half looked like bare, uncoated porcelain, sort of like those continuous cleaning ovens that were out there for a while. I took the agitator out of that machine and found a fist full of mop head lint underneath it, as if the machine had been used to wash floor mops, probably with lots of cheap detergents.