Doesn't the Big Gold Belt date back to like 1905?
I will preface by sayiing I'm not a professional wrestling historian (I'm sure one of those guys on this board will correct my errors and/or omissions) but here goes as far as I know without doing any additional research...
The Big Gold Belt dates back to 1986, where it was brought in to replace the NWA World Heavyweight Championship belt, also known as the "Domed Globe" belt as the new iteration of the NWA World Heavyweight Championship. Since the Big Gold Belt now represented the National Wrestling Alliance, it inherited the history the previous championship belt had, like the Domed Globe version did of the belt it replaced and so on and so forth.
The National Wrestling Alliance traced their World Championship back to the days where professional was known for the Catch-As-Catch-Can style where guys like Strangler Lewis, Frank Gotch and Georg Hackenschmidt ruled the day. The 1905 reference used through the years on NWA and WCW programming is a reference to what many considered to the first and original professional wrestling world heavyweight championship.
When WCW started using the Big Gold Belt to represent the WCW World Heavyweight Championship in 1994 after the unification between the 1991 established WCW World Heavyweight Championship and the Big Gold Belt, which in the past was recognized as the NWA World Heavyweight Championship, for a brief time as the Big Gold Belt then finally as the WCW International World Heavyweight Championship, they adopted the history from the NWA World Heavyweight Championship to their own WCW World Heavyweight Championship since before WCW became what it was, it was an NWA territory under the Jim Crockett Promotions banner.
When WCW talked on their programming about their World Heavyweight Championship dating back to 1905 I believe it goes something like this...
1. Original Professional Wrestling World Heavyweight Championship [circa 1905 era]
2, NWA World Heavyweight Championship [established in 1948/1949 I believe].
3. WCW World Heavyweight Championship [established in 1991. Ric Flair is commonly referred to as the first WCW World Heavyweight Champion while he was still in his reign as NWA World Heavyweight Champion with the Big Gold Belt being used to represent both Championships, although Lex Luger was the first person to win the actual physical WCW World Heavyweight Championship belt that would be used from July 1991 through 1994 where it would be unifed with the Big Gold Belt, where from there the Big Gold belt was used to represent the WCW World Heavyweight Championship until the company's closing in 2001].
Although the lineage gets a little murky with the splintering of championship belts, unifications and all that has happened over the past 100 years or so in professional wrestling.