I use Cole. I've had one claim on a gun lost in shipping and they paid up, minus the $500 deductible and the $100 that UPS PAID. Now I insure with the shipper for $500 to cover the deductible.
What's to stop the primary insurer from deducting the $500 payment from their portion? "Other insurance" clauses can bite. Is the shipper's insurance specific enough to get around the insurance paid for the deductible? Insurers do what they can to benefit themselves. For instance, a homeowner insurers his $500,000 home for $250,000 and suffers damages of $250,000 but it is not a total loss. The insurer reduces proportionally its payment and doesn't pay the $250,000 but considerably less. To get the $250K, the house must be insured for $500K. Gil
Pay heed to Gil's advice. During my 45 years as a CPA I read a lot of insurance policies and the majority (vast majority) have both "other insurance" and "co-insurance" (you don't insure the property for full value) clauses.
I just read my Hanover Insurance Group policy and it does have an "other insurance" clause. The way I read this policy as applied to the situation you describe they will reduce their payment to you by the deductible.
Example:
10,000 loss
( 500) received from carrier insurance
----------
9,500 remaining loss
( 500) deductible on primary policy
---------
9,000 net payment to you
500 from carrier insurance plus 9,000 from primary insurance = 9,500 = the same amount you would have received without the carrier insurance.
Not reporting the carrier insurance received to your insurance company is likely insurance fraud. I'll let Gil answer that one, as I recall he was an attorney.