Agree with the above posters...most likely 30 amp. Even my new unit, which is a 50 amp AC RV, the battery cable is fused at 30 amps. The wiring for the 12v loads shouldn't exceed 30 amps (due to wire size) no matter what the trailer itself is wired for (AC). Anything higher than 30 amps on normal 12 volt wiring will cause overheating, melting and possibly fire.
That being said, I have always replaced my 30 amp fuse with a 30 amp circuit breaker. You still get the same 30 amp protection, but, with a circuit breaker if you accidentally short the line, the breaker will pop, but, just like your house, it can be reset. If you develop a "short" and it pops, you can reset it while you look for where the short is as opposed to going through a bunch of "one shot" fuses while looking for the short. You can get the 30 amp circuit breakers wherever you find the fuses (usually) and they plug right in the same as the "one shot" fuses.
My 2 cents, your mileage may vary...
2 Cats; J-Lo and Ragamuffin :R
2014 Thor Tuscany 40RX DP
2011 Ram 2500 Longhorn CTD HO
2011 Keystone Cougar 318SAB (now gone)
2008 FunFinder X 210WBS (Sadly gone)