Identify Valve Lap Tool

[JAKEFORD]

I have an old valve lapper. It is a crank handle style similar to a speed wrench. The valve end is swivel fork with two small nipples that engage holes in the valve. My guess is its from the 1920's.

The tool is rusted and the identification is hard to read. The no is 608 but no manufactuer name. There is a symbol M in a diamond which is probably the manufactuer trademark stamp. The tool is in nice condition except for some rust spots.

Can anyone suggest who made the tool?