A reasonable price for a border engraved only SLE today with no more than what you have listed about the gun--absence of bore condition, whether in proof, 2 1/2 inch or 2 3/4 inch chambers and wall thickness is unknown and one cannot estimate the price. One can see that the exterior of the barrels of this Hussey are poor, so I suspect the gun is of little value. If it has bad barrels (bore, wall thickness and proof problem) the value is zero. If it has bad barrels then the oak/leather case is worth more than the gun.
Here is a link to a Atkin SLE gun of similar engraving (or no engraving) of known quality by a respected gun dealer in Scotland; and if you convert the price from UK pounds to USA dollars it is about $4,000.00. You can buy it and have it shipped to you for less than $800.00 ( a shooting colleague of mine just bought one from Graham and it cost him $709.00 to have it shipped to his local FFL shop. English guns are priced to sell in the UK, but the USA gun dealers are still pricing them high because they bought them at a high price.
https://www.gmackinlay.com/product/12g-ad-ejector-by-henry-atkin-28-x-2-1-2-barrels/
