I have this book and have started collecting these guns.  As I have seen more and more examples and accumulated more knowledge I am discovering many many errors in Cope's information.  It is a good book and probably the best guide to these guns but be aware that it has lots of errors.  I believe Cope based the info in the book on what he could observe from limited examples, original Stevens catalogs, and on feedback that collectors provided him.  Unfortunately, there are no factory records to work from and surveys are not very reliable if the sample size is to small.  Stevens collectors on this forum:  I was wondering if the same experience with his info has been discovered by you all as well.  
Examples:
Stevens Gould frames being exclusively iron  - definately not true
Production numbers which don't seem to coincide with the number of guns for sale.
Barrel stampings of the company name as it changed through time.
Firing pin types especially with regard to the Conlin and Gould pistols
and there are more.
Red

The book ( out of print and around $75-$200) does not cover the Stevens line of single shot rifles only pistols and pocket rifles with removable skeleton stocks which Stevens called "rests".  There is a section in the back which reprints the 1897 catalog and it features their tip-up rifles and also a section which reprints the telescope catalog from the 1908-1910 period.  If you want a reference for rifles I would suggest the book "Savage and Stevens Arms Collector's History" by Jay Kimmel.  It has lots of info on the 44, 44 1/2, and boys rifle lines including many reprints from several Stevens Catalogs and is reasonably priced.  The Stevens Catalogs can be purchased from Cornell Publications and are outstanding and fairly inexpensive.  Several of these are well worth investing in if you collect or are interested in Stevens.  I think there is another thread currently on this forum that also discussed Cornell Publication.
Red

The Gould and #35 issue is the most difficult.  According to Cope the Gould must have a bushed firing pin and a serial number below 25,000.  He states that all #35 pistols have serial #s above 25,000 and all Goulds have serial #s below 25,000.  I have found this to be true.  However, Cope also states that Goulds must have a bushed firing pin as the #35 had the cross screw retained firing pin.  There lies a contradiction because there are both Goulds and Conlins of later production which have serial #s below 25,000 that have the cross screw retained firing pins and not the bushing retained pins.  I have seen many of these guns which are definately Goulds or Conlins.  My most recently purchased Gould has the bushed firing pin, a serial # 12,4xx, the windage screw adjustable rear sight, checkered grips, but it has a brass frame.  He states Goulds all had iron frames.  At first, I thought it might be a Conlin.  Cope states that Conlins had both iron and brass frames and that someone removed the spur from the trigger guard but the trigger guard is not messed with  and has the slightly different shape of the Gould trigger guard with the matching last 3 digits of the serial # stamped on the inside.  All the numbered parts on this gun match.  It is certainly original.  Maybe there were some brass frames unused from Conlins that were used to make Goulds right at the beginning of Gould production.  I have no idea what the earliest Gould serial # is but I would not be surprised if mine is close.   
Also, you can see some differences in checkering styles on the early Lords, Conlins, and Goulds as compared to the later ones.  I think this may be due to a change in craftsman doing the work.  I have not seen any catalog illustrations showing the later checkering styles.
I am out of space.  To be Continued maybe with photos if folks are interested.  I am to long winded.
Red

I did not mean to say the Cope book is not a valuable reference tool.  It is the best on this subject available.  I just keep finding examples which are contrary to some of the info in the book that appear to be honest correct guns.  I will post photo of guns that I have found which support these issues.  Its always fun to look at photos.  I will try to learn how to put them in my post instead of on photobucket.
Red