Single-line or outline.
Letter height = 0.25" <-- well, at least that was easy
Leading if two lines are vertically adjacent to each other.
Kerning if the letters are horizontally adjacent to each other.
Method of "engraving" e.g. laser, machined with a cutter, heat ribbon stamped etc.
..If machined with a cutter
...."v" or Straight or ball-end or what?
....Diameter of cutter.
....Max flat at the base of the "v".
....Included "v" angle.
....Max and min cut depth.
If the lettering is on an arc, whether it is base-line, center line or top aligned.
The list could go on for each important parameter. If a parameter is not important to YOU, then don't state it as it will just add unnecessary expense in conforming to specifications.
Generally, I will not give you the answer to your question, but I **will** guide you into discovering how to solve this yourself.