I don't know what date they changed, but
Talley shows "current production" bases for Dakotas as 8-40 thread as opposed to 6-48. With that serial number you probably have a 6-48 threaded action. Should be simple for you to check what size yours is if you have an extra mount screw hanging around.
FYI, some mounts (Talley bases) are left or right hand specific because of the bolt release lever.
* I used Talley steel bases with 6-48 screws on mine but not sure how old it is because it was serialized by a custom maker