I posted a comment on your thread on the the Bolt Rifle Forum. I'll add another comment in response to your question here.
For $300 you did well given especially since a 3200 was included. I see older Mossberg bolts guns every now and again. Examples in the condition of yours are typically in in the $300 range and not very far under that amount.
I picked mine up about 2-3 years ago at a gun show for $199. I snagged it as soon as I finished looking it over. By that time there were two other fellows waiting for me to put it down. I mounted a old Weaver K4 on it. The 810 actually looks a bit new for the K4. The K4 actually dates back to the '50's. I'm giving some thought to replacing the K4 with either a steel tube Tasco 3X9X32 or a Redfield 4X32, both of which I purchased around 1975. The Gun Traders Guide shows the 810 was manufactured from 1967-79.
From the info I've found indications are that action is rather strong. The weak link seems to be in the attachment of the bolt handle. The locking lugs require a bit of camming. From what I've read the handle isn't attached very solidly and can break loose during the operation.
