1950s GE Toaster tray doesn't stay down--science needed!

Hello Hello,

I've got a 1950s GE toaster that I found, and have been refurbishing in my spare time.

I've gotten everything to work except that the tray won't actually stay down. I'm guessing it might be a solenoid problem. But here's the thing: I have no idea how to test whether my solenoid is working or not, as I know not much about how an electromagnetic field should behave in various states.

When my toaster is actually on, what readings should I be getting on my multimeter which would inform me whether my solenoid is still working? Where should the prongs of my multimeter actually be? Am I going hot wire-ground? That's how you do it in a car, but how do you do it in a toaster! Holy smokes!

Here a some pictures of a the toaster in question when opened up, Apologies for the poor quality. The first image is front facing, the second one if taken from below, with a clear view of the solenoid.

Thanks a whole bunch!