I bought a partial set of North Ingermanland stamps at my local stamp club tonight. I was able to pick up Scott 1,2,4,8-14. I really like these. What I found really interesting is that this "country" only issued 14 stamps total.
Yes, Mr. Cypel, the treasurer of the stamp club vouched for their authenticity. He knows his stuff. He listed the cat. Value for this partial set at $60.
Large quantities of these stamps were remaindered in 1922 to a stamp dealer when the stamps were no longer valid. CTO's should be considered remainders. Genuine used copies are not common, and are worth much more.
The cancel on the stamps in nl's post is the CTO cancel.
The forgeries were made in the 1950's, and may have come from Great Britain. There is some vague information that the forgeries were sold to collectors in Finland. It is believed that these forgeries (since the stamps were not worth very much in the 1950s) were made, along with other forgeries (like Iran), for the packet trade.
The easiest way to tell the forgeries is that they were printed on very white paper, while the originals were printed on cream-colored paper. There are other very easy to find characteristics to identify forgeries from the genuine stamps as well. Some stamps that appear to be CTO remainders could also be forgeries with the CTO cancel.