This is the deluxe model with the slot, although the box has label stating standard, the below information has been taken from Richards website.
Standard dovetail mark without slot, deluxe version with slot to act as try square to aid marking out. Slope per edge 1:5 for softwoods, 1:8 for hardwoods. Solid brass 2-1/2 inches overall. Superb quality.
Price is inclusive of postage to mainland U.K.