Preban Essentials were marked J-15. All of those were cast, most gray, a few black.
Postban Essentials are marked J-15-2. Again, most gray, a few black.
Beginning in November, 2005 Vaughn was going to begin making forged, and drop cast. He told me that there were no problems with his INVESTMENT cast lowers, but he was going to forged just due to customer requests. He was going to discontinue cast, sell out what was left, and from then on all production would be forged.
Essential also makes very high quality aluminum CAR stock assemblies.
There were a number of companies around the country that used Essential lowers, such as early Bushmasters. There were some companies that were making full auto lowers for law enforcement on Essential lowers.
No complete rifles left the shop except for a few hundred he built for competition shooters.
In my experience, the EA lower I owned some years ago, all parts fit and functioned perfectly. I have also seen and worked on many other people's AR's built on EA lowers. NONE had a malfunction that was due to anything about the EA lower. I have never seen, nor know of anyone who has seen a broken EA lower.
I have three EA lowers now, last of the cast ones.
Other than that, I don't know anything about Essential Arms.