Here is a summary of the types and production numbers:
2.8GX-First Model, Synchro-Compur-X shutter, 10,200 produced between 8/87 and 3/94 2.8GX-First Model - Rolleiflex 60 Year Commemorative, Synchro-Compur-X shutter, 1,500 produced in 1989 2.8GX-First Model - Helmut Newton Edition, Synchro-Compur-X shutter, 500 produced in 1994 2.8GX-First Model - Expression 94, Synchro-Compur-X shutter, 500 produced between 3/94 and 95 2.8GX-First Model - Gold Expression 94, Synchro-Compur-X shutter, 33 produced between 5/94 and 12/94 2.8GX-First Model - Japan Edition, Seiko shutter, 130 produced in September 1995 2.8GX-Second Model - Rollei 75 Year Edition, Synchro-Compur-X shutter, 900 produced between 1/95 and 12/95 2.8GX-Second Model - Expression, Copal shutter, 1,000 produced between middle 95 and end 96 2.8GX-Second Model - Club Rollei Jersey, Seiko shutter, 100 produced in 1996 2.8GX-Second Model - Royal Edition, Seiko shutter, 1000 produced from 1996-2000
The primary difference between the first and second models is the strap hanging arrangement and the meter battery enclosure design. The latter is cosmetic only. The first model has a strap hanger mounted toward the rear of the body and accepts the same type strap as the SL66 and SL2000 cameras. The second model uses a hanger that is found on the System 6000 cameras.
Because each sub-type of the GX was produced in such small numbers each tends to have some sort of collectable cachet. Our esteemed listowner is an ardent fan of the GX. I personally prefer an 2.8E2 or 2.8F. The T* coating does produce higher contrast images under trying conditions but under normal conditions the results are equal. I, personally, find the GX to have a somewhat tinny feel compared to the E and F cameras. Others opinions differ. The metering is certainly more accurate than the old meters and the TTL-flash metering is clearly an advantage. Only shortcoming is getting the ungainly SCA356 mounted in a sane way.