Texas, USA: eBay seller OEC Camera have listed two AC/DC studio flashes manufactured by Mettle. The 300AD and 600AD are 300J and 600J Bowens-mount flashes operating on 110VAC or an included 16VDC battery pack. They are similar to the Adorama Flashpoint M and Quantuum R+ Dual Power series.
The Kurbster (who supplied the picture above) has written a hands-on review of the Mettle 600AD which can be found here. The specifications are the same as the Quantuum R+ Dual Power with exception for the AC voltage:
Quantuum R+ Dual Power
|Recycle, AC/DC||1.5 / 5.5s||1.5 / 5.5s|
|Pack||Battery Pack||Battery Pack|
|Aliases||Mettle 300AD, 600AD - Proxistar PS-300C|
|Retailers||Foto-Tip (PL) - Photo-Shop-Studio (AU) - Mediaresort (DE) - OEC Camera (USA)|
The Mettle 300AD and 600AD are priced at $257.75 and $298.25 respectively at OEC Camera.