I bought it on eBay and it arrived today.
3-5/16 wide x 3-1/4 tall x 22 long, double iron, body and cutting iron marked Mathieson. It is in great shape, and will be a good user. Someone named W. MacLachan put his name on it, as can be seen.
I am thinking of putting a strike button into the fore end. Would that ruin it?