27-7 is not a part number. It is a model number and an engineering revision. It does not identify a specific firearm

Nobody knows how many 27s of the -7 engineering revision were manufactured. Production counts are maintained by product code, not engineering revision.

We do know that 100 of product code 170166 and 100 of product code 170167 were all produced during the -7 revision of the model 27.

Many product codes span 2, 3 or more engineering revisions.

As to why a particular revolver will sell cheap, the answer is easy the seller does not know what the demand and current market are for that item. Not everybody lives on the internet and looks at auction prices or posts to the various boards. I am often astonished at what some people pay for things in other parts of the country and that is not even mentioning CA

I bought an 8 3/8" model 57 from a local gun shop last summer. It was pinned and recessed with the faintest turn line. They had it marked $700. I offered $475 out the door. Non-plastic guns do not sell well at this shop and they do not post on the internet so I check their used case often. They turned my offer down. Every time I went in there over the next several months I made the same offer. It is now in my safe with my other 41 Magnums and I paid $475 OTD for it.

I can not tell you how many deals I find in small pawn shops.