Unable to identify the builder/manufacturer of this MVB

[RD]

Anyone have any idea?  I know Griner engraves his plates.  The only identifiable feature here is a #13 stamped on one of the plates (see pics).  Got this off of ebay due to the intriguing anodized metal covers and thought it was an interesting valve body to investigate.  The throttle pressure valve is not activated by the lever, so I know it is a MVB (or at least assuming at this point) as I have not taken it apart.  Hoping that someone may have seen this type of valve body from a manufacturer to shed some light on who sold it originally.

thanks.