An intersting research challenge. Based on the info here and other searches I am adding a Shiro entry on 
www.jedistar.com as follows:
Shiro guitars, Japanese made in the 1970s. Copies of USA classics Les Paul, SG, 335 etc. plus some original shapes.
One guitar mentioned at Vintaxe had  a manufacturers label, which reads:
CONSTRUCCION ARTISTICA
DE
GUITARRA
SHIRO
Model No.576N
Made in Japan
A German forum suggested a link with Aria as Shiro is of course the first name of the founder of Aria.
I did a Google search of the label information as the spelling is quite unique. Many other forums across the globe report Shiro guitars with a similar label and a variety of model numbers.  Interestingly I came across the following label at Delcamp forum.
RYOJI MATSUOKA
LUTHIER
CONSTRUCCION ARTISTICA DE GUITARRAS
ANO NO. 50 NAGOYA JAPAN
The NO 50 is handwritten." 
Note the following observation "For a few years during the 1960s and early 1970s , Matsuoka produced the higher end Aria guitar models for Shiro Arai, founder of Aria . These Aria models either have Ryoji Matsuoka's name on the label or are marked RM with a red stamp on the neck block.   [Source: Orozco Guitars]
This is evidence in the direction of the observation that Shiro guitars were made by Matsuoka. Of course Matsumoku had a very significant relationship with Aria as well, but the similarity of the Matsuoka label pushes me in that direction.
Reviews 
http://reviews.harmony-central.com/revi ... rand/Shiro
-----------------------------------------
Any other suggestions???