I would go to the Williams gun sight company.They should have a chart that will answer your question for you.
Yes, on certain models. Around serial number 1600000 and beyond.
It means that it is a Model 1890 (90) receiver. When Winchester introduced the Model 1906, they used the exact same receiver and action as the Model 1890, with exeption of the cartridge carrier. To readily differentiate between the two, Winchester stamped an "A" on the Model 1890 receiver and a "B" on the Model 1906 receiver. Bert H.
Receiver
On the receiver
Receiver
Receiver.
Check the receiver.
Receiver.
Bottom of receiver
Check the receiver and barrel.
Check the receiver.
Bottom of the receiver