Your cancel is a portion of a "duplex" handstamp cancel (the circular date stamp and the killer are duplexed or paired together), made of steel, so often called a "steel duplex" cancel. Here is a more complete example on a card and a handstamp device, showing the curvature of the killer matches the circumference of the entire device.

The red line is a natural part of the plate manufacturing and explained here. These are hyped upon the gullible on
ebay, but are neither rare nor valuable:
https://stampsmarter.org/learning/I...reLines.html