Another history lesson from a 19 year old here? Yes, there were too many changes before the open era, when we went from wood racquets in the nineteenth century to wood racquets in pre-open 1967. In the open era we've gone from wood to metal to fiberglass laminate to ceramic to boron-reinforced graphite to graphite-fiberglass to graphite-kevlar to....what's next? Pre-open wasn't international? Huh? Roster of players from the 50s and 60s includes prominent players from every continent except Antarctica, including notable players from India, South Africa, South America, Eastern Europe, and of course Europe, Austalia and the U.S.