[Mod: This topic has been split out from another thread (see link below) as it gives important new information.
http://www.glassmessages.com/index.php/topic,55910.msg316923.html#msg316923]Hello everybody,
lastest news- received a very friendly reply from Ed Poore, who was employed at Pairpoint - he had a gentleman, Carl Otto Schweidenbach as his polishing and engraving teacher, and remembers this time with respect and gratitude- so a signature "COS" on facetted or engraved items can be related to Carl Otto Schweidenbach without doubt- for certain customers he did eventually sign his work.
Thank you, Ed Poore, for this important background information, I am not sure if the signature is well known to the collecting community, but by now it should be known: COS- Carl Otto Schweidenbach, master engraver, polisher and tutor at the Pairpoint Glass Works...
Kind regards, Erhard
...pictures of details will soon be uploaded...

..the signature once shows inverted but well in the look-through view...