OK, so it's basically a half conversion. Since most field coils are in series with the armature, the "conversion" would reduce the current draw slightly by using a higher resistance field. We used to call those "high torque" starters when a custom rebuilder would go the other way- - - -putting 6V fields in 12V starters for high compression race engines.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!