Yes, it is. The 600AT was simply sold under the New Haven name instead of the Mossberg brand. It's a Mossberg 500A (12 gauge) intended for targets and hunting (long barrel and great wood). All Mossberg 500 parts fit it.
No
All.
If you have a 500, and it is a 12 gauge, it is a 500A. The "A" designates it as a 12ga. A 500B is a 16ga, a C is a 20ga, and an E is a .410.
No
It means you have a Mossberg Model 500a shotgun with the serial number L109563.
Yes.
It can be, if you are using a slug
You will have to call the company to find out.
175-350 USD
They are the same. Mossberg 500 series includes all shotguns. 500A is 12gauge. 500E is 410.
The Mossberg 600CT is a model based on the Mossberg 500 design with some variations. The 600CT is specifically designed for law enforcement agencies. While there are similarities between the 600CT and 500A, such as the pump action mechanism, there may be differences in features or customization options.
50-250 or so