Hello Rose, and Welcome to WAGS !
I had to set your profile for you, sorry for the Delay.
I also had to dig to find an answer to the question you asked!
What you have is Cast Aluminum, not Magnalite.
The 378 is a 'Heavy Duty Two Compartment Mess Pan" which was part of the Wagner line of INSTITUTIONAL items.
I had to wade thru many Wagner Catalogs, and finally located this item in a 1939 HOTEL Ware catalog.
During this time period, these items were marketed for sale to Prisons.
"All Virgin Aluminum"
Values are difficult to predict right now, as the 'market' is fluctuating quite wildly on a daily basis.
Hope this helps!