Citation:
The Historic Division started in 1993, but didn't get in to full swing until 1994. Gibson made a variety of "Reissue" guitars prior to this. Apparently, these were built on the regular production line. However, my experience is that the Reissues were of very high quality, better than the "regular production line."
With the Historic division, Gibson embarked on producing Les Pauls that were more similar in construction to the originals. That included a change to neck/body join, bringing back the "long neck tenon." The "tenon" is the tongue of the neck that intrudes and is glued into the body of the guitar. The originals and Historics have a "tenon" that goes into and under the neck pickup cavity. If you pull the neck pickup, you can see the intrusion (there is usually a gap where the tenon ends). The "Reissues" prior to 93/94 did not have that. That would include the 1992 '54 Custom Reissue.
That having been said, the "Reissues" are very fine instruments. The 54 Custom Reissue that you have features a mahagony body with no maple cap. That's a cruacial part of the early Custom sound. The neck pickup is a true Alnico single-coil. For some reason (probably to avoid hum), they fitted a P100 "stacked humbucker" pickup in the bridge. It looks just like a P90, but is in fact a different humbucking design.