A neat idea for using 'washers' to stamp the names.
Hope that the washers are of a good quality and/or protected metal though (no rust).
Punching letters is a rather tedious job; but is ok for small quantities.
High quality 'numbered' tree-tags already exist, but one must be sure to have a
'number/name' reference list saved/available somewhere. This is my way to go.
I am also thinking of color code spraying these tags for easier hunting (say in 25 multiples).
The above mostly applies and is essential to potted/movable trees.
(Yes; I do have a few 'orphaned' figs due them tags fading/etc.)
For in ground trees, tags may also be desired/required, but
nothings beats a 'map' on a piece of paper showing 'what is where'.
[Trees do not have legs and are not able to flip locations.]