1. This is more-or-less a standard Reitz slide rule layout.
2. Blundell not only sold rules under its own brand name but also produced them for other manufacturers. I have identical rule made for W H Smith a chain of newsagents and stationers.
3. This rule was one of the rules which the manufacturers had left on their hands when people stopped buying slide rules.

Front view

Detail - front left

Detail - front right