I also have a WGO26S...the CE model. If Washburn ever wanted to call a guitar a "mini-Jumbo", this ought to be the one...same large lower bout and small upper bout, slope shouldered, and deeper than many dreads.
As for production numbers, I'd suspect that weBgUy might be able to help out...back when WBNick was moderating the forum he gave me production info on my C124SWK.
I have often wondered about the info in Washburn's serial numbers and have found a pattern that seems to be consistently applicable.
For example, the serial # on one of my WMJ21S guitars is CC101124069. CC is a designation for one of the Chinese factories...10 indicates the guitar was made in 2010, 11 stands for November (11 th month), 24 is the 24th day, and 069 means my axe was the 69th to get off the production line.
110708165...first two numbers mean made in 2011, next two indicates 07th month, 08 indicates 8th day of the month, and 165 means your guit was #165 to roll off the production line that day.
I have checked all my recently made Washburn guitars and there are none for which this pattern has not worked.
My WMJ21S has no serial number on the neck block, but there have been instances where the serial number on the neck block and the serial number on the paper label are significantly different. We have a very knowledgeable member who has explained that phenomenon and has also done some mining in Epiphone's production archives and knows which city CC would be... I'm working off my cell phone and can't figure out how to copy URLs, but I'll see if I can locate those two threads and edit this post with their location on the forum.