According to the parts book I have for the B, shutters were used on tractor serial number B43301 and up. For serial numbers B101 through B43300, a curtain assembly was used. Prior to B101, nothing was used. My '42 B is serial B58812 and has the original shutter assembly. They do get rusted up and frozen. Mine had not been operable (frozen open) for many years until last summer. I took it apart, sandblasted it, painted it and got it back in operation.