This looks to have been polished recently. The undermount is 21mm and the collar is a standard 39mm Duplex. The item "Original Cranberry Cut Glass Oil Lamp Matching Shade Font 39mm collar 21mm umnt" is in sale since Sunday, March 25, 2018. This item is in the category "Antiques\Antique Furniture\Lamps\Victorian (1837-1901)".The seller is "rodders923" and is located in Midlands. This item can be shipped worldwide.