Today, I purchased these 1926-1927 "Map of the U.S. and Two Mail Planes" stamps from a local coin and stamp store. I couldn't help but notice that the gum has ink traces. I read that at the time, newly stacked sheets could still have wet ink and would transfer it onto the gum of the top sheet. Please feel free to stick your gum to this thread.
The technical term is set-off (or setoff). Not unusual on early 20th century US flat plate printings. The ink is not actually on the gum, but on the back side of the stamp underneath the gum. On flat plate press printings, the gum was applied long after the ink dried. This is why you will sometimes find setoff ink on the back of used flat plate press stamps. Your 3 stamps do appear to be "natural" set-offs that happened during the production run. But hard to say for sure without physically examining the stamp.
If the ink is on top of the gum on flat plate press stamps, that is not production setoff, but damage caused by stamps being stacked/stored on top of each other under pressure in humid/hot environment. These damaged stamps are considered gum damaged should be heavily discounted by the seller, even if they claim it is never hinged (it's actually considered worse than hinged). If you don't care about gum, you can save a lot of money.
Set-offs are rarely found (although not impossible) on early 20th Century US rotary press printings. In this case, the ink is actually above the gum! Rotary press stamps with set-off on the gum are often considered a (minor) defect, but like straight-edges, that's really in the eye of the collector.
Thank you for your detailed reply khj. I'm going to attend a stamp club meeting on Tuesday and find out whether these examples were defects from the manufacturing process (I hope) or from poor care by the previous collector(s). Will get back to you on that.
I purchased them for 5 bucks a piece and chose them because they look to be centered well enough. Plus I'm into historical aviation.
Today, I purchased these 1926-1927 "Map of the U.S. and Two Mail Planes" stamps from a local coin and stamp store. I couldn't help but notice that the gum has ink traces. I read that at the time, newly stacked sheets could still have wet ink and would transfer it onto the gum of the top sheet. Please feel free to stick your gum to this thread.
Posts: 1,636
What I collect: I collect world wide up to 1965 with several specialty albums added due to volume of material I have acquired. At this point I am focused on Canada and British America. I am always on the lookout for stamps and covers with postmarks from communities in Queens County, Nova Scotia. I do list various goods including stamps occasionally on eBay as hdm50
Stamper49, as per what hdm1950 stated, the landing gear is there. I also took my magnifying glass to it and confirmed that.
khj, the first local meeting I will attend is on the 14th. I was mistaken about it being held this past Tuesday. Hopefully, someone there can determine if the gum has set-off ink.
I attended my first local club meeting and members agreed with your assessment that the stamps are from "natural" set-offs that happened during the production run. Many thanks for your explanation.
Posts: 291
What I collect: 19th Century US, High denomination US (> $1), 19th century covers US, Indian Feudatory States and most recently I acquired a BigBlue [with about 5,000 stamps] and pristine pages.