There's an article on the Winchester Model 54 in "The American Rifleman" a few years back that I read over about 50 times. . It's very imformative and describes all the running changes, upgrades and the transition to the Model 70. . The time frame on the early M54's was when Winchester was running into receivership and the Olin Family (Western Cartridge Company) was taking Winchester over. . Winchester new the M54 had a few defiencies but was not financially able to correct them . When Olin took over Winchester, these issues were addressed. . The triggers were upgraded and called the 'new speed lock" and the gas issue was also addressed by drilling a hole in the front of the receiver to allow gas to escape if case ruptured.. . You could send your early M54 back to the factory and Winchester would correct these issues. .
The later M54's were used in the development of the new up and coming Model 70 . . The last few years brought out the "NRA" stock, that continued on with the Model 70. . The bolt handles were changed making them scope friendly. Many early Model 54's were returned to the Winchester factory for the latest upgrades as they occurred during production. . The bolt on Noel's gun as well as the gas escape hole drilled in the receiver and improved trigger would be my thoughts on where these upgrades were done . . These upgrades were common, in the day, and is something to be thankful for and improves the value rather than take away from it. . Can you imagine getting Winchester to do these upgrades now. .