Ca. 1975 Gruen “Big Triangle” 200M Diver - Ref 754 - powered by a 25J, ETA 2783. Some may call this a Gruen “Explorer II” based on the dial. Gruen most certainly shared Stern Freres as a dial manufacturer with the Rolex, specifically for the Explorer II - Reference 1655. Interestingly, Rolex purchased the Gruen Precision Factory building after their closing in 1976.