Technical Stewart Warner tach with bronze extension, what is it?

This is an old Stewart Warner convex glass hand-held tach (408858) that is coupled with a 6" cast bronze extension that has mounting holes and a 90 degree drive....does anyone have any idea what this was used on?.

 

Might be for an industrial application, doesn't look automotive.

 

interesting. i've had a couple of those hand held sw's, but never seen an adaption like that. google the part number with sw included, may bring up something. i see no oil hole, so it must not have run full time