Sorry to hear about your dad. I have found a little information about your watch. It's a beauty cannot believe the price in 1974!
The Calibre 1510 was most famously produced with an aventurine crystal dial, nicknamed the ‘Stardust’. The watch came in a number of variations of dials: stardust (silver and gold), waffle dial in black, blue and brown and electric blue dial.
The total production run of calibre 1510 was also 1000 units, around 800 of which were produced in stainless steel with a variety of dials and 200 were produced in solid 18 carat gold (weighing over 200 grams) with either stardust or electric blue dials.
The original list price in 1974 for a calibre 1510 was £604 in stainless steel and £3275 in 18 carat gold, by contract the Moonwatch was £134!