CA insurance is different than most - if not all other states, with our no fault + independent insurance commissioner & requirements for each insurance company to be approved to sell in state.
We were recco'd in 2012 to go with "Flo" / Progressive for Agreed Value on our restored vintage kin 1960
Avion T20 by the resto guy who did the PPI for us, but Flo had stopped writing Agreed Value policies by then - at least in CA.
So we stayed with AAA & they added it at the Agreed Value based upon the "opinion of value" given by the PPI guy (he's not an appraiser), & never got an appraiser to do one since they accepted it.
Now I need to get an "opinion of value" report from GoWesty for our restored 1988 VW Westfalia, since most appraisers don't know that market & hopefully AAA will switch that to Agreed Value thereafter - or at least their ACV will be based on a realistic value & not just a beater or good survivor Westy.
I do have good claim history on the cars for over 33 years (plus a prior stint in the 1970's - early `80's on my Porsche 914 until they stopped insuring sports cars for a time) with AAA/ACSC (Auto Club So Cal) - but nothing with the Avion so far (cross-fingers!).
For vintage trailers - & once your newer AS/TT reaches that "Classic" age - it's a good idea to get a new appraisal every 2-5 years, since their values go UP/appreciate - NOT down/depreciate - with time & even with a resto & use "aging" the trailer, due to market demand increasing for the vintage trailers.
That trend may or may not continue, but it's worth watching out for your investment's coverage.