+1 to what harleyhouse said - the A1 variant had the surge brakes on the tongue. Your trailer, Max, is an original M416. There is no way to determine the year from the data plate, UNLESS the month and year of manufacture is stamped into it. If the rear data plate is missing, or the date isn't stamped, I can't help you.
When I rebuilt my M416 in 1998, I got the axle seals and bearings from NAPA. I just went by the info stamped on the parts themselves, and the NAPA guy was very helpful.
The blue paint you have on there is not original. Now, it could have been an Air Force trailer if it was blue, but a much darker blue called Strata Blue. Could the blue paint you have be Strata Blue in a very faded condition? Maybe, but I doubt it.
There are no sources for used military tires in good shape. The majority of jeeps and jeep trailers were auctioned off by DRMO in the 1970s through the 1980s. Maybe some tires and parts got let go in the 1990s as well, but that's almost 20 years ago. The only source for tires now are new repro tires, which for safety sake is your best bet anyways. The proper size is 7.00x16 NDCC. You can get them here:
https://www.universaltire.com/truck-and-military/military/700-16-firestone-military-ndcc.html
or here:
Firestone Military NDT - 700-16 - Miltary/Truck