Things like this just go to show that you should never take for granted boxes of commons you have around. As you progress through the hobby you begin to learn things about the insulators you have, and didn't necessarily appreciate previously.

The N.E.G.M.CO. CD 145 on the left has been in storage in the barn for about 4 years. I dug it out yesterday, and one look at it officially dubbed it the piece with the most dome glass of all insulators I own! There is a full 1 3/8" crystal ball of shiny glass over top of that pinhole. And to think, yesterday you couldn't have seen the colour of the insulator it was so covered in dust!

All the best!