When I was a kid, I worked at Office Warehouse (now Staples or whatever bought them). We sold lots of 'Signature Stamps', which were simply a custom-made rubber

When I was a kid, I worked at Office Warehouse (now Staples or whatever bought them). We sold lots of 'Signature Stamps', which were simply a custom-made rubber stamp with your signature on it. IIRC, the customers that bought them were business owners who needed to sign lots of checks. I'm pretty sure this was both normal and considered legal in the US.