Glass compression style radio antenna strain insulator. Embossed very weak PYREX BRAND in one groove, 66000 in the other, etched AP.53024 on the side, and has a tiny dot on each end that may be vent drips. Has a light vaseline tint, is 2-1/4 inches long with one very tiny tick on one edge, three very shallow chips, and a factory ground flat spot on the side, also has a tiny carbon floater in the glass and some tiny bubbles. This is an uncommon strain that was used by the British military. $75 gets it shipped, thanks.