These certainly were NOT boy's pistols or parlor pistols.
They were intended for the 50 yd slow fire precision match governed by the United States Revolver Association.
Hence the name USRA pistol.
If you are unfamiliar with these please have a close look at the cross section diagram I posted above. The trigger mechanisms work the same but the position of the return spring, sear engagement, and fulcrum points are different. The hammer geometry is also different.
You could achieve a safe 1 lb trigger with reliable ignition.
H&R hired Walter Roper and gave him free reign to design the gun. Not surprisingly, Roper designed several grip options for them.
However, for all of it's qualities, they never were truly competitive with the best European single shot "free" pistols, such as the Üdo Anschütz Rekord of Rudolf Hämmerli's MP33.
These pistols had true micrometer sights, extremely fine set triggers adjustable to a fraction of an ounce, very fast lock times, and even better anatomical grips made to measure for a glove-like fit.
Nonetheless, for their intended purpose, a single shot designed for competitors whose primary arm is a revolver, the H&R USRA pistols are exceptionally nice.
Jim