It's a little focus jig used to set up the distance between the lens and the material to cut.

Made from a similar jig observed in use with a Trotec Laser.

Actually used with an HPC Laserscript 6040.

Tweak the source file for your setup or if your focus distance is not 41mm.
Cut or Print.

Lower the bed.
Hang the focus-jig on the lens washer.
Rise the bed until the jig fall.

Voilà :)