Young Brothers steel stamp set.

[Highpower]

This is what they say about their rounded profile stamps.

Quote:
Round Face-Full Character Hand Stamps
The cutting edge of the character is 1/32" radius, with a 40° bevel. Rounded character stamp makes low-stress impressions suitable for use anywhere metal strength is critical. The aircraft, missile, oil supply and nuclear power industries depend on these stamps to avoid risk of fracture from too sharp an imprint.
Character identification and size, three thumb grooves.