Well, my guide that I used is know totally gone. I should have made a mirror of the site...
There used to be a site that had some pretty good records for serials vs. manufacturing years but it went down a few years ago. The Internet Archive had a copy of it but now it isn't working anymore.
What is your serial? Can you post a pic?
From what I searched:
- 26300 is from around 1995
- 8283 Autococker is circa 1992
- 9351 is a 1991 serial (which contradicts the above serial but idk)
- Mine is 134687 which is 2003 for a fact (probably too new for what you are asking)
Sometimes when people mini their cocker, they cut off a part of the serial number making some people think they have a really low serial. Also, any cockers that came mini from WGP have a different numbering system. Like 1069 is a 93 and 3896 is a 97. Also, some private labels used their own serial numbering system, from what I've heard.
You have pre-2k and 2k+ bodies. Slider frames are classed at pre-98 and 98+. Bodies are easy to tell since the front block hole is a different size (+2k is bigger, trilly is even bigger) and the really old bodies are pretty obvious. Slider frames have to be disassembled to look at the trigger plate shape. Of course that doesn't help if the frame isn't stock.
Is there anything special about this gun? Any logos from private labels? Just go to imgur.com and upload some pics and post links. Maybe someone can help.