I got these in an estate sale box. One is stamped "Imperial Brass Mfg Co Chicago USA  Patent Applied For". The other is stamped "Imperial 5/8".  Imperial Eastman makes tubing fittings and hose fittings. The first one is a hand operated hollow mill that makes a taper that is blunt on the end. The second is used to thread onto something and then mills a taper with a blunt end. Question is; what are they used for?

They look like tools I have used to cut new surfaces on damaged flared hydraulic fittings. The threaded holder fits on the fitting and the cutter creates a new sealing surface.  Does the cutter on the left fit into the threaded holder? Maybe they are for two different flare angles.

I would agree that it is for repairing the flare seats on brass fittings.  Should be for 45 deg. Flares.

It looks like the outer threaded portion should be free of the inner portion.  That way you can screw it on to the damaged fitting and turn the tee handle to reshape the flare. 

The one without the outside shell might be an extra, if the same size as the other one, or maybe you use it free hand if the flare isn't munged up too bad.

Just an idea.

Mike

Male flare fitting refacer.
The collar threads onto the fitting and aligns the cutter.
They come in 37½ and 45° flare faces.

The cutter was made to recut brass, NOT steel
There should be multiple alignment sleeves in the set to cover a spectrum of fitting sizes.

That tool will save your a$$ when you have a leaking fitting and no replacement.

Imperial Brass just rocks!
My favorite tube cutter of all. My ratcheting flare nut wrenches. Best tube benders I ever used, and my best flaring tools.
All Imperial!!
 
Still in business too. What a class act.

Stride owns them now.
http://www.stridetool.com/index.html
  yours Scott