For the price a 1 watt laser is worth the risk, it supports windows 10 and it's portable. 1 Watt or 1000mw should be enough to overcome the small curve of the pen, but as in all engravers, the top side will be deeper than the edges. I fill the engraving with acrylic paint from my daughters art kit, looks great.
This 5.5 W seems interesting but it does not support windows 10 and the board is bought separately, although it may be able to engrave the ruler lines on a piece of plywood. 5500mw A5 Mini Laser Engraving Machine-391.48 | GearBest.com
As my father would tell me "as soon as the frog grows hair" I can have it!