For several decades beginning in the mid-1950s, some Plumb handles were secured with a plastic resin adhesive called Permabond. This red, slightly pliable material is an epoxy blend. When used with hickory handles, the wood was tapered to be a tight fit at the bottom and a very loose fit at the top of the eye, allowing the Permabond to flow around all sides of the wood. No wood or steel wedges were used. More information and a cross section is on Google Patents. If you have never read a patent and its technical language, check it out (a hammer is a "percussive tool"):
US Patent 2850331
US Patent 2850331
To remove a handle with Permabond, cut it off close and do not attempt to drive it out. Drill as much out as possible going from the top and bottom, especially in the center. I recommend a dust mask. Sharpen an old flat bladed screwdriver, making it into a chisel. Using the screwdriver and a punch, remove material from the middle and work outwards. Place the screwdriver at the edge of the Permabond and begin prying and chiseling the Permabond loose from the steel. With luck, you'll find that the steel has rusted a little and weakened the bond, and the Permabond will come off in big chunks.
For more information, you can read this post from Blade Forums on the same subject:
The same procedure may work on other epoxies.