Your stamp is from the edge of the watermark mat, where the paper manufacturer had their watermark: KPV (KONGL POSTVERKET). What you are seeing is the last 3 letters "KET".
These are considered "collectible" to some specialists, so it would be to your benefit to properly ID the stamp.
Thank you khj
The stamp appears to be Scott # 77. I do not see any other watermark. So I am thinking that this is Unwater marked paper showing the margin watermark.
I have scanned the stamp.
Doug
re: Sweden Definitive Types 1910-1919
Your stamp is from the edge of the watermark mat, where the paper manufacturer had their watermark: KPV (KONGL POSTVERKET). What you are seeing is the last 3 letters "KET".
These are considered "collectible" to some specialists, so it would be to your benefit to properly ID the stamp.