I am in the automobile insurance business although I do not sell to the public. My experience includes working with national account partners in the specialty markets, including old cars. Most folks would be surprised to learn that very few antique auto insurers actually underwrite their own risks. Most are mainline carriers who "hand off" risks like antique auto to other companies who actually assume liability...of course for a price. We are the re-insurer for many companies, meaning that carrier "A" will only underwrite liability and physical damage coverages to a certain limit and anything above, they hand off to the other company (us). To the customer, coverage is seamless and any claims are handled by the company doing the billing.
For most specialty carriers, they will underwrite to liability limits of $300K Combined Single Limits BI/PD and $500 deductibles for Comprehensive and Collision. Any BI limit that's higher and/or any Comp/Coll deductible that's lower is usually reinsured by another carrier.
The "rule" where vehicles need to be in a garage is common to most antique and specialty auto market carriers. Because older cars are more difficult to repair or replace due to parts availability, parking in a garage greatly reduces their exposure to theft and the elements. The mileage restriction keeps owners from using them as regular transportation. Policy exclusions stating they will not pay if a claim originates from regular use don't stand up in court so the restriction was developed to curb (pun not intended!) everyday use.
And with nearly 20 year's experience in the business, I've seen it all. We had a claim filed by a vintage Chevy owner who hit a cow. He claimed he hit it driving to a show two days after buying a policy from us. Our adjuster located the cow's owner who had a police report of the hit three days prior to the claimant's policy purchase. The claimant said he hit a different cow (really?!) but the adjuster found the car's hood "V" stuck in the cow's abdomen. We denied the claim because the car owner didn't have a valid policy with us at the time of the hit - and he was stuck with a sizable bill for the disposition of the heifer.
