The early (before the 1960's) IJ revolvers didn't have model numbers, only names like "Target" and "Protector." The .22's were all 8 shot and the term "Sealed 8" indicated a system where the cylinder had flanges front and rear so that side flash or gas from a burst case rim would be contained.
Later, IJ did make a solid frame .22 revolver that sort of resembled a SA, called the Sidewinder (Model 50). Other solid frame models were the 55A (Target), 55SA (Cadet), 56A (a starter pistol), and 57A (Target).
I don't recall if the Model 50 had that marked on it or not.
Jim