What are you trying to ask? Maximum range or maximum effective range?
The Winchester Model 68 bolt action single shot .22 was made from 1934-46. It did not have a rear sight mounted on the barrel, but had a receiver mounted Winchester No. 96A peep sight (books at $20-40). As options, Winchester offered the Lyman No. 55W or 57ES Receiver Sights ($25-75). The hunt for old gunsights can pretty interesting. Lyman is still in business, and may be of some help. Good luck. By the way, the rifle (with sights) books from $275 at 100% to $50 at 60% condition.
Answer Guns made prior to the passage of the National Firearms Act of 1934 were often made with muzzle threads for the attachment of a sound suppressor. I have an early Colt Woodsman threaded for the Maxim suppressor which was the most popular sound suppressor of that time period. Winchester Models 1890 and 1906 are occasionally found threaded for suppressors as well. Possessing a firearm threaded for a suppressor is perfectly legal. Owning an actual suppressor is legal in many states provided all National Firearms Act regulations are followed.
Cornell Publications has books on H&R
I'm not sure about this but i remember seeing somewhere on the internet the value was from $75 to $125