Got this information from Australian Camera Dec 2000 issue:
R4 unveiled at 1980 Photokina, share some body parts with the Minolta XD-11.
R4s appeared in 1983 and was a slightly cheaper version minus the program and shutter-priority auto modes, but retaining the choice of metering methods with the aperture priority auto exposure control.
R4s mod 2 in 1986 introduces some ergonomic improvements including an easier to use exposure compensation facility. The mod 2 also had improved film transport controls (chiefly a stronger rewind crank) and a slightly revised viewfinder display.
Buying do's and don'ts:
don't buy one of the earlier samples. These are marked "R4-MOT Electronic" with serial numbers starting in the sequence 1 53X XXX to around 1 54X XXX and are plagued with electronic problems. Some of the early cameras badged just "R4" may also have dubious reliability so look for serial numbers starting 1 55X XXX and beyond.
One problem is bubbling effect which occurs on the top plate of both the chrome and black finish models.
Hey if you want to see the article I can pass you the magazine. Realized it doesn't really specify if the country of origin makes a difference.