Firstly, thanks to all for their kind words.
#5892 should date from around 1890 and can be considered as a relatively early boxlock for Blanch. It will probably have a stepped action (looks like a Greener) but will be pure A&D inside. The barrels will most likely have been Damascus originally but if steel will most likely be dovetail lumps and not 'Fluid Steel' whatever the top rib says. Having said that, a few do turn up with replacement genuine Whitworth item - look for the 'sheath of wheat' trade mark under the forend.
The engraving will usually be of 'ordinary' quality scroll, reflecting its probable origin of Birmingham where it was most likely made and finished. If the engraving is more special, it may have been finished in London but I have never seen one of this vintage that looks like a London gun.
Original wood is usually pretty good but replacements are often real 'planks', again reflecting the percieved value of the gun.
As to whether this gun is a good buy, I would be rather worried about the 'light weight'. These guns usually run 6lb 8oz to 6lb 12oz and so it could be that the barrels' wall thickness is not too good. Get it measured before you part with a $.
Overall, later Blanch boxlock guns were 'finer' finished that many of their contemporaries but these early ones are often a bit plain. Don't forget that after nearly 120 years, the internals may be a bit sad!
If you do buy it, please send its specification via the questionnaire at http://www.jblanchdatabase.co.uk for inclusion in the database. Please also send a photo or two 'under seperate cover'.