1950's Era Precancels

Has anyone ever run across stamps precanceled in black over another color? I have a US #1040 that appears to have been precanceled in violet or purple than precanceled again in black. The picture doesn't show it as well as the naked eye.

Or the black ink contained magenta or some other pigment that's visible in the bar.

Gentle request: Please show the entire philatelic item, then show any additional close-up scans to clarify the question. It is important to provide full information and put the question in context. Thanks so much!

This appears to be a "local" precancel applied by hand (the importance of showing an image of the entire item), and essentially impossible to apply the cancel device twice in exactly the same position. Thus I have no doubt this stamp was only precanceled once. Also with a mix of inks, perhaps along the lines of ... we need to precancel these stamps and I can only find a large inkpad with magenta ink. Oh well, I'll just add black ink to the pad and it will work fine. Nobody will ever notice if it has a little magenta too.