38 ACP Half-Moon Clip (Drawing)

To keep myself busy in this time of being discouraged from leaving the house I’m sorting through some long neglected corners of my computer and its various back-up hardrives … so much stuff and interesting what one saves then never looks at again. Something I found yesterday is this drawing of a half-moon clip from 38 ACP dated 1933 and it raises a question in my mind.

To use a clip like this the rear face of the revolver’s cylinder has to be rebated to accomodate the clip … why would anyone do this when ,38" rimmed cartridges weren’t hard to find and anyway, the 38 ACP cartridge was something of a “minority interest” and offered no advantages over anything else on the market.

Does anyone recognise where the drawing might have originated from ?