They have a "social media" site listed. I suggest you try there.
The specs on Heil AMTs are fairly well documented if you search the net, though you may find some conflicting statements. Efficiency is very high (>97 dB) and the impedance is just under 4 ohms and very flat across the band. They are current hungry and not crazy about tubes.
They always sell out on their sales and waiting is common, but eventually they do deliver.

