(full-size image: 120 kB)

This rule has the standard scales K A[B CI C] D L but with the non-standard designations that can be seen in the illustration. The back of the slide is blank.

There is a model number S.101 and the text MADE IN ENGLAND on the front, but there is no manufacturer's name on the rule. The back of the rule is blank except for the text

HADRIAN
SMITH & WALTON LTD.
HALTWHISTLE

which is probably the name of a firm which gave away these slide rules as publicity material.

The C and D scales are 5 inches (12.7 cm) long.

This slide rule was probably made by BRL (Blundell) in England. It is very like the BRL model P15 rule illustrated on Ron Manley's web site here.