Originally Posted by 2152hq

A cylinder assembly from the H/S Sentinel may work in the Double Nine revolvers. They are the same guns with different outside appearances.
The DoubleNine was a re-work of the Sentinel starting in '58 or 59.

The very early Sentinel cylinder will NOT work (mid 50's production) as it has the 1st style ratchet on the cylinder back side. Easy to spot as it is simply 9 evenly spaced shallow holes, all about 1/8" in dia. Each with an accompanying small channel cut towards the center pin.

Wether they actually do fit and the ejector rod is the same ect,,I do not remember. Not a lot of action working on any of these over the years. But just a though that may widen the field in a search for a 22lr cylinder.

Some research may help settle the question.

The Double Nine made for the 22mag and 22/22mag convertible was a steel frame version. The Model number was the 106, came around in the mid 60's IIRC.
Earlier 22lr only guns were alloy frames, model 104. But sold under a bucket of fancy names as the finish and features changed.

Early guns had a firing pin on the hammer. When the 106 steel frame was intro'd, they went to a transfer bar w/firing pin setup.

AFAIK, they never marked the convertible cylinders with caliber markings. It was just the Mags don't fit in the LR cyl,,and LR's are a loose fit in the Mag cylinder. You figure out which one you have.
Different time I guess.