I have not ever seen that particular style of decal for Cobb. But it does potentially look to be of the era (from the early teens, if authentic).
While the lack of H & B Oval may be a legitimate concern, Goldin just auctioned a Wagner Mini Bat purported to be a Salesman's Sample (with no H&B logo). It was a clean and magnificent example, and even had the accompanying Felt Carrying Case...
http://www.goldinauctions.com/1910-1...o-LOT7629.aspx
That Wagner, however was 14" long, as compared to 12" for this Cobb. I don't necessarily think any of these factors (unique decal / lack of H&B Logo / 12" length) are deal-killers, and think we probably would've seen more of these, if reproduced. But look forward to hearing others' opinions as well.
Exceptional looking piece, regardless!