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This.
In my experience it is incredibly difficult to maintain alignment of the letters - even when using angle-blocks clamped to the workpiece.
Also, you need to keep the stamping pressure equal on each letter.
I found the best way of doing the latter was to punch a dimple into the tail end of the number punch, and then apply the pressure using an automatic centre punch, placed into the dimple and dialled to the pressure you desire/the material dictates.
I think the easiest way to DIY is with a standard set of letter stamps which would do the job fine. You're only issue will be getting every letter nicely aligned, but that depends on how picky you / they are.
https://www.amazon.co.uk/AmazonBasics-Metal-Leather-Stamp-Kit/dp/B0783J7PFM/
I think you'd need to find a piece of metal you don't care about that is the same thickness as the blade to wedge into the handle whilst you are stamping, otherwise you will distort it.
Only other thing you'll need is a big hammer and a sturdy bench. Enjoy!