I will upload a series of pics. These look like round drip points to me. RDP is not listed for this type insulator. There is a side that has an under pour. Wondering if this is RDP or simply result of glass being hot and not developing? The drips on this are so well rounded though I have to wonder.

There are only 5 other pictures of the Gayner 620 on ICON and all have very prominent SDPs. Seems to be a somewhat scare insulator(?)

Would like feed back on the possibility of being RDP and also would love to have information on areas of use and years these units were in production. I had never seen one till my last show and so I bought.

THANKS for you help!