Redesign of Worm/Line Guide System.
Penn redesigned the worm, line guide and bearings, replacing the design on the original run of reels (early 1980s).
HOW TO TELL IF YOUR REEL HAS THE OLDER SYSTEM:
The most distinguishing feature is the BLACK PLASTIC LINE GUIDE.
The second is that the older 50-330 worm shield was closed off on the ends, using in different bearings than the newer reels. Both versions use the same pawl #47-975.