IF your appraisal does not explicitly state the brand, and it's not explicitly stated on the policy as well, you will not get exactly what was lost (i.e. Tiffany for Tiffany). So make sure that is identified.
As for Chubb, I am pretty sure it is on a case by case basis and based on location. My ering is not anywhere near 40K in value, the total of all my insured items on that policy is probably half of that, maybe, and I have standalone jewelry policies. My friend is also on a standalone policy, which she started within the last two years, though her ring might be valued at almost 40K as it's a pretty amazing monster. My sister's ring was not valued high enough to be considered for a standalone policy IIRC, but her husband I believe put it on a rider with their homeowners.