Chad Gripp (Gripper) had a Triple Lock that had been converted to .22LR, as show in this thread: https://smith-wessonforum.com/s-w-h...g-rifle.html?highlight=triple+lock+conversion
In post #39 of that thread, I showed pictures of a 1917 that I had that'd been converted to .22LR also.
And here's a Model 10 that had been converted: Model 10 - chambered for .22LR
And a Model 3 top break converted to a single shot .22LR: Tulsa gun show haul - Nov 2011
There is also this thread, which has a converted .455 that looks very much like the OP's gun: Questions about .455 webley to 22lr conversion revolver

In post #39 of that thread, I showed pictures of a 1917 that I had that'd been converted to .22LR also.
And here's a Model 10 that had been converted: Model 10 - chambered for .22LR
And a Model 3 top break converted to a single shot .22LR: Tulsa gun show haul - Nov 2011
There is also this thread, which has a converted .455 that looks very much like the OP's gun: Questions about .455 webley to 22lr conversion revolver