The No.1 uses a spring-loaded plunger that press up inside the barrel channel. I have a dozen found examples I'll share for free for asking.
The spring tell me, and someone who knows No.1s will have to jump in, that the barrel is arched upwards between the breech ring and the nose cap. The No.4 has downward pressure against the bottom of the foreend. Different mechanism of tuning.
Yes, it's a a lot simpler, and a very quick fix when it works.
Just cut and trim the cork sheet to fit the pad in middle of the barrel channel, the forend and top handguard, put it all back together and go to the range.
Ted