I read the thread you linked to on shotgunworld. Here is something to consider....you sound like you intend to sell the gun and are trying to ascertain value. One poster on the other thread gave an estimate in Britain of $2000 USD, and suggested that the retail price in the US might be double that.
Canada, GB and the US are all distinct markets. There are legal barriers to the free movement of firearms between them, the result being that they stay distinct. The Canadian market for firearms such as yours is significantly smaller and less vibrant than the US market, resulting in significantly lower realized prices.
If you want decent advice from participants in the Canadian marketplace join Canadian Gunnutz and start a similar thread in the sporting and hunting shotgun thread. You'll get good, local advice about the real value of your gun in the market you live in. A significant draw for membership at gunnutz is an buy and sell section called the EE. With 150,000 gun owning members, it gets the item in front of the potential market quickly.
BTW, I own a lovely J & W Tolley. I think very highly of them. But the market for English boxlocks with Damascus barrels is pretty weak. Were I to guess, I think you would do very well to realize an amount over $1500 Cdn. But that's just my thoughts....post on gunnutz and get 10 others' opinions.
