The First Winchester'66 ?

[Henry4440]

This is the earliest known serial number and based on the records is possibly the very first Winchester  produced.Winchester 1866 First Model Nimschke Engraved SRC .44 RF s/n 12476 mfg 1866 - 20” round barrel; full mag; straight grain walnut stocks; crescent buttplate.

A link:http://www.rarewinchesters.com/gunroom/1866/M66-012476/66_12476.shtml
Compare the s/n with the Henry rifles.Very interesting.
 

[Grizzly Adams]

Maybe.  I saw two model 1866s that were being offered by an antique dealer in Alaska.  They were consecutive  serial numbers.  The first was fitted with a barrel bearing the Henry barrel address.  The second was marked with the Winchester barrel address.  According to the documentation, that example with the first arm marked as Winchester.