MK-1 it is..
on 8th of December of1936 two pilots broke word record for navy bombers. They had 10 000 kg of weight (ordance) picked up to 1942 m (6 000 feet)
But others flight <not registered as word records> had weight up to 13 000 kg.
Heavily defended by a few cannons and MG's the plane was awefuly slow and had very bad climb rate.