It's handblown from borosilicate glass

Now Admiralty Chart 2631

The brims are plastic (not cardboard)

and the whole instrument oriented in the meridian by means of a magnetic compass in the base

DexShell Terrain Walking Socks, Black/Grey Size:Small It's handblown from borosilicate glassConstructed with DexShell's patented three layer, four way stretch technology, the Terrain Walking Socks are woven with merino wool yarn for both the inner and outer layers. This creates an authentic, luxurious feel with the utmost warmth and performance, as well as the anti blister and anti microbial benefits inherent in merino wool. These waterproof and breathable mid calf length socks are designed with a cushioned bottom and elastic arch support,