Anyone know the size/type? I have one coming with a missing speaker.

I have one on the hold bench awaiting recapping. I can take a measurement over the weekend and post the results.

Thank you so much! That would help very much.

As per the manual, 5" PM Speaker

My NC-57 had low and distorted volume due to a frozen voice coil. The heat from the nearby output tube probably helped cook the speaker over the years.
I used a replacement Jensen 5" car speaker and mounted the audio transformer to the chassis. The magnet on the replacement speaker was a little larger and the fidelity is now pleasant to listen to.

There were a few versions of the NC-57. Mine has the output transformer mounted on the chassis. The main dials are also different. The replacement dial on Radio Daze does not match the one on my receiver. It's a fine radio with a circuit similar to the NC-125 but without the built-in Select-O-Ject audio filter.

John VE3PMA

What was different about the dial? (Never mind, I just noticed that it is an 'M'). I think that Radiodaze also offered the NC-57 dials in green? Mine are amber.
It is a hot, self-contained receiver and was a decent value in its day. Great for broadcast listening.
I do miss the S-meter, but it isn't that critical. The NC-33 was the sparsely equipped one in this family.
https://www.eham.net/reviews/detail/2700