My understanding was it was the original Isospeed (Or Classic that it is called now)
Player Racquet Mains Crosses Tension Event/Year Source
Muster, Thomas Head Prestige Pro Isospeed Isospeed 68-71/68-71 Roland Garros 1991 USRSA
Muster, Thomas Head Prestige Pro Isospeed Isospeed 81.5/81.5 U.S. Open 1991 USRSA
Muster, Thomas Head Pro Tour 280 Mid Isospeed Isospeed 86/86 U.S. Open 1994 USRSA
Muster, Thomas Head Pro Tour 630 Isospeed Isospeed 90/90 Roland Garros 1995 USRSA
Muster, Thomas Head Pro Tour 630 Isospeed Isospeed 90/90 U.S. Open 1995 USRSA
Muster, Thomas Kneissl Tom's Reach Machine Babolat VS Power 17 Babolat VS Power 17 79/79 majors 1996 USRSA
Muster, Thomas Kneissl Tom's Reach Machine Babolat VS Power 1.30 Babolat VS Power 1.30 86/86 U.S. Open 1997 USRSA
Muster, Thomas Isospeed Isospeed 38/38 Newsweek Champions Cup 1999 Star Stringing (Chris Lundquist, CS)
Muster, Thomas Head Isospeed nylon Isospeed nylon 31/31 Roland Garros 2009 Tecnifibre
Muster, Thomas Head Isospeed nylon Isospeed nylon 34/32 Roland Garros 2009 Tecnifibre
Muster, Thomas Head Prestige 600 Isospeed Professional Luxilon Alu Power 1.25 57/55 Australian Open 2010 Wilson