Thanks for the reply's so far, I'd first like to address that I am not the least bit insulted of upset if this shotgun is only worth $40.00; surprised would be more likely I had figured it must be worth at minimum $150.00. At least I don't have to adjust my firearm insurance

. My intention is to restore and display this so if I have over spent on it that is quite fine. Sure it would have been great to unearth a long lost treasure but I had my doubts that it was when I bought it and paid $100.00 less than I would have so I remain quite comfortable with my expenditure.
The engineering pics should be quite helpful as I restore this piece I appreciate then very much. I had already searched this site and others for Teschner, Collath and Tesco, there is a very limited amount of info posted on the web about this company as far as I can tell.
In regards to the 1880ish guess: would it be safe to assume that by that era Collath was a partner and as such his name likely would have appeared on firearms of that period as well? Or am I misunderstanding how they utilized their names?
Any other guesses as to approximate age and value are welcome, also any speculation on the significance (or insignificance) of only Teschner's name appearing on the barrel. As well as any info regarding this company, including reputation etc.
Also I would not be apposed to firing this if there is a source for the correct cal 1 ammunition.
Thanks again for your ongoing help.