Tool is marked "Hinkley-Myers SE839-4 magneto armature bearing puller".
So I knew what it was, but I wondered what make/model it was to be used for.
I originally mis-read the # as "889" once I got it right I found out is was for IHC F-4, F-6, and E4A mags (and perhaps others).
And that would make it pretty darned old!
The bolt heads have no markings.
Here it is in use, key # 8.,..
As an interesting side-note, my internet reearch sems to indicate that "Hinckley-Myers" has a connection to the "Kent-Moore" tool company of today.