I believe you mean Lyman #358156 bullet mold. I don't know of anyone offering it commercially, you have to cast your own. Lyman still offers this mould, in solid or hollow point.
It was designed in the early 1950s, when .357 Magnum brass was very difficult to find. By using .38 Special brass, and seating the bullet out and crimping into its lower crimping groove, the bullet approximated the same case volume in the .38 Special as in the .357 Magnum.
This particular cartridge -- with the .38 Special case crimped into the lower groove of the .358156 bullet -- is intended to be fired ONLY in .357 Magnums. They can take the pressure.
For .38 Special revolvers, this bullet should be crimped in the upper groove and a standard .38 Special powder load used.
The 358156 bullet was designed by Ray Thompson of Grand Marais, Minn. He also designed it to use a rifle's .35-caliber gas check, a novelty at the time. Later, pistol bullets began to be designed to take a variety of gas checks.
Elmer Keith had nothing to do with the .358156 design, nor with the design of the classic semiwadcutter, which dates to the early 1900s.

Keith improved upon the established semiwadcutter design, by having a front driving band that was wide to better align the bullet in the chamber throat as it headed toward the barrel's forcing cone.
To my knowledge, Keith never designed a gas-checked bullet. He believed in bases that were full caliber, not beveled, with wide base bands.

The late gun writer Skeeter Skelton wrote an excellent article about his use of the Lyman 358156 bullet -- in solid and hollowpoint -- in the 8th edition of Handloader's Digest. This book may be found on internet auction sites.
Skelton's 1978 article prompted me to buy a Lyman 358156 mould in 1979, for my Ruger Security Six. Been using that bullet since. In a good gun, it can be a tack-driver.
Lyman also offers this bullet in hollowpoint form, but you have to make them one at a time: rather tedious.
The 358156 remains one of the best bullet designs for the .38 Special or .357 Magnum. The only downside is that if you assemble .357 Magnum-power loads in .38 Special cases, you're playing with fire.
Sooner or later, someone may drop that cartridge into a .38 Special and experience what we reloaders call an, "instant disassembly."
Today, there's no point in using .38 cases with this bullet to get .357 Magnum velocities. Brass for the .357 is readily available.
I stopped making .357-power loads in .38 cases years ago, fearful that I'd somehow load a .38 Special with such a load and wreck the gun or harm myself.

This bullet does not eliminate the ring of lead left in .357 Magnum chambers when using .38 Special cases. It's the case length that creates the problem, not how far out the bullet is seated.

Excellent bullet. If you cast, or want to try casting bullets for the .38 Special or .357 Magnum, the 358156 is hard to beat.