What are the differences between Bianchi's X1500 and X2100 series leather shoulder holsters?

Is either still in production?

Apparently these holsters' spring retention translates to flexibility of what handguns the holsters accept. Please identify specific model numbers or identification of X1500 and X2100s that accept Colt SAA revolvers. I anticipate more than one holster number for each basic model will accept this revolver frame size and configuration.

The holsters are different models, but they appear to have similar features? Differences I think I detect is that some?? X1500s have safety straps, and some?? X2100s have thumb break strap. Relying on my memory, I'm uncertain this information is accurate. I'm uncertain, if accurate, its relevance.