it signifies that it is one of the earliest models
By: ei8htohms : January 14th, 2008-02:52
Hi daytona 1712,
The gold/steel crown was only used on the modern Type XX for a few years (at most) when the model was first re-introduced in the mid-90s. As such, it identifies your watch as one of the early examples, something that collectors will likely value over time.
Whenever you send it in for service you'd have to request that they not change the crown if you want to keep it though. The crown is often changed to insure proper water resistance, but from a collectability standpoint it would not be a good idea for your watch.