Here are a couple links to H&A ser#'s/yr mfgr charts.
They are approx and stated so.
Kind of confusing.
The revolver in the OP is an 'XL 8'
So states on the top strap as well.
The XL #8 was made from 1877 to 1885 according to this ser# chart.
It was ser#'d in it's own bloc of #'s aside from the rest of the XL series of revolvers which ran XL1 to XL7.
There was an XL30 as well and it was also ser#'d in with the #1 thru #7 XL.)
In this chart which shows the separate XL series serial numbers
The serial numbers only go as high as '2700'
Hopkins & Allen
Obviously the OP's gun is higher if the number under the bbl is THE ser#
Many of these are ser#'d under the grips on the frame.
This second link is for the XL series all together. #1 thru #7.
**The ser# chart does NOT include the XL#8 (it is ser#'d in it's own bloc above link))
Plus, the #1-#7 revolvers serial numbers were started and then restarted again and then a third time over their production life.
XL
H&A's production history is vague at best. No records remain of course and it is a posterchild for the 'Never Say Never' phrase.
I believe that the #8XL was made after the 1885 cut off date in the first link ser# chart.
AND that H&A may have started ser#'s over again in the same pattern as done with the #1-#7 ser#'s.
I think the authors of the XL8 ser# chart just lacked that following yrs production info or not enough to approximate for an educated guess.
The XL8 was made after 1885. Likely for the same time that the rest of the XL line was made and that was into the 1900's
H&A went bankrupt , going out of business in 1898.
Reorganized, they came back in 1899/1900.
Pre-bankrupt (1898) they were 'Hopkins & Allen Company'
Reorganized after above, the company was renamed and became
'Hopkins & Allen Firearms Company.'
The two slight name differences are often used to determine 'Antique' or 'Modern/C&R' firearms status with the lack of any factory records.
They made a lot of TB revolvers as well.
Their drop bloc single shot rifles are nice. The 922 series and the centerfire calibers made on the larger drop block actions that are an intermediate size to their large drop block shotguns are all nice rifles IMO.
I restored a nice Mod 3922 (Jr Schuetzen in 22cal) some time ago. A similar configuration the the Stevens Lady Favorite Target rifle.
Should'of bought the H&A 12ga drop block single at a show this past weekend. Nice shape,,but too much stuff around now