Deka batteries are manufactured in eastern Pennsylvania. A contractor with whom I work is a Deka rep over in western New Jersey. He puts the batteries in his backhoes, excavators, dump trucks, haul trucks, etc. and swears by them. He is willing to sell me any Deka for his cost.
A few years ago I bought a Group 27 'dual purpose' Deka Marine Master from him for my last boat, a Beneteau 343. Supposedly the dual purpose battery gives the benefit of a deep cycle battery with the cranking power of a starting battery. The price was right and the battery seemed ok - my house bank was 2 of these and the engine battery was a single. (Of course I figured that anything that is a dual purpose generally gives the benefits of neither with the drawbacks of both.)
I later priced the Deka golf carts when I upgraded to a Rolls 325 amp-hr lead acid battery. Even with his discount the cost of cabling, boxes, and fittings raised the overall cost such that the Rolls was more cost effective. I went with the Rolls & was very happy for the single season I used it.
Regards.
DH