Date of purchase vs clasp serial.

[Capf2005]

Sorry for the question friends. I'm just confused. I own a Pre-Owned GMT.

Serial S (1993)
Clasp Date T12 (December 1995)
Date of rolex certificate (purchase) - September 1995.

I know that the date of the serial may be different from the date of the bracelet, but the purchase date being 4 months before the date of the Clasp (T12), does it make me believe that the bracelet has been replaced or do these date anomalies occur?

Excuse my English, it's not my native language.

Cheers

Augusto.