These rackets are undoubtedly THE most popular non-wood players frames ever.
The Pro Staff 85 has been used by some of all-time great tennis pros including Chris Evert, Steffi Graf, Stefan Edberg and Pete Sampras.
Sampras used this racket throughout his professional career refusing all efforts by Wilson to get him to use newer models or at least make his racket look like a newer model through use of a paintjob on it.
Federer used this racket as well but it was disguised (paintjob) as a newer model.
These rackets were originally manufactured at Wilson's River Grove plant near Chicago.
In an effort to cut down on production costs, Wilson moved production to a new facility on St. Vincent Island in the West Indies.
Rackets made at this facility have been assigned mystical qualities by many players mainly because these were the only that Sampras would use.
It is unlikely that there is much difference in quality between the Chicago and St. Vincent versions other than the addition of bumper guards to the later St Vincent rackets.
In the early 90s, Wilson again moved production; this time to China, again undoubtedly to cut costs.
The early China versions had problems with quality control. Later versions are of higher quality but purists are mot convinced that they measure up to the Chicago or Saint Vincent rackets.
Below is a table showing, to the best of my knowledge, the different versions of the Pro Staff Midsize rackets and their distinguishing characteristics (also see legend below the table):
Chronological order: order in which model was manufactured with respect to time
Legend for the Table above
"name"
PS = PRO STAFF
6.0 = PRO STAFF 6.0
"code location"
refers to the bottom or top of "W" on buttcap
"MIDSIZE"
written on outer edges of throat
x2 = writte on both sides
x1 = appears only on one side
85 = MIDSIZE 85
"origin"
SV = Saint Vincent Island, West Indies