Midsize 85 Wilson Pro Staff 4 1/2 grip in 9/10 outstanding/near mint condition.  This is an late production run St. Vincent racket with BYQ buttcap code.  Pete Sampras' rackets all came from late St. Vincent production runs such as this.  Check out the photos and my Pro Staff Guide (below) to confirm that this racket is the real deal. specifications:grip - 4 1/2headsize - 85 sq inwt. - 366g/12.9 ozbalance - 8 pts HLstring - wilson nxt mains/luxillon big banger original crossesquaxrax's Guide to Pro Staff Original midsize/85 models/versions.  These rackets are undoubtedly THE most popular non-wood players frames ever made.  The Pro Staff 85 has been used by some of all-time great tennis pros including Chris Evert, Jimmy Connors, Aaron Krickstein, Jimmy Arias, Mary Pierce, Steffi Graf, Stefan Edberg, Jim Courier 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 started out with midsize Pro Sraffs, black buttcap China version, whih in late 2001 were disguised (paintjob) as a the newer model (HPS 6.0 , the first of his 90 sq in headsize rackets) that he adopted in 2002. Pro Staffs were originally manufactured at Wilson's River Grove plant near Chicago.  In an effort to cut down on production costs and,reportedly, improve quality control, 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 rackets produced there were the only rackets that Pete Sampras would use throughout his entire professional career.   In the early 90s, Wilson again moved production; this time to Taiwan and China, again undoubtedly to cut costs.  The later Asian versions are of high quality.  However, purists are not convinced that they measure up to the standard set by the "legendary" 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):

chronol. order	NAME	BC	CODE	CODE LOCATION	MIDSIZE	BUMPER	TENSION	PRIMER	FINISH	ORIGIN
1	PS	WHITE	xxI	BOTTOM	X2	NO	65-70	RED	MATTE	CHICAGO
2	PS	WHITE	xxQ	BOTTOM	X2	NO	65-70	RED	MATTE	SV
1a			xxB							BELGIUM
3	PS	WHITE	xxQ	BOTTOM	X2	NO	55-65	RED	MATTE	SV
4	PS	WHITE	xxQ	BOTTOM	X2	YES	55-65	RED	MATTE	SV
5	PS	WHITE	xxQ	BOTTOM	X2	YES	50-60	RED	MATTE	SV
6*	PS	WHITE	xxQ	BOTTOM	X1	YES	50-60	RED	MATTE	SV
7	PS	WHITE		TOP	X1	YES	50-60	GRAY	GLOSSY	TAIWAN
8	PS	WHITE		TOP	85	YES	50-60	GRAY	GLOSSY	CHINA
9	6.0	WHITE		TOP	85	YES	50-60	GRAY	MATTE	CHINA
10	6.0	BLACK		TOP	85	YES	50-60	GRAY	MATTE	CHINA

* there should be line 6a identical to line 6 except butt-cap code Qxxchronol. order: order in which model was manufactured with respect to time name:  PRO STAFF or PRO STAFF 6.0 code location: at bottom or on 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  NOTE - in the blank row there sould be mention that some pro staffs were briefly produce in Belgium by Donnay with buttcap code xxB.