Canadian Excise Stamps & Postage Issues With Revenue Cancels

I didn't look for another thread on this topic but perhaps someone could give me some advice.

A local ex-collector owns a large accumulation of cancelled cheques and bills with George V excise stamps of various denominations and a lot of George V and George VI postage stamps (including many Admirals), most with revenue cancels. There are at least two cartons of them and he is looking for someone to appraise them. I only had about 20 minutes to examine the contents and don't know much about these stamps. I will have another chance to examine them more closely in a few weeks. There look to be some interesting varieties there from a quick look but I need to know a lot more about them before I can offer him any advice. Some of the cheques are not in good condition but many of the stamps appear to be OK. Should they be soaked or better left on piece?

Since they are revenue uses, the stamps would be best left on piece.

I agree - revenue cancels are non philatelic and of almost zero interest to collectors. Also - seems to me there are tons of cancelled cheques around with no market for them. Only possibility I'd see there is they were from small, obscure and now closed banks. There is possibly value in stamp varieties though but that requires expertise to find and evaluate.