What a great example, you don't see many solid 18K versions anymore (there are probably less than 50 remaining worldwide) and certainly not in this lovely original condition. Your example is a peach, the bracelet looks very tight and the dial looks super, what a great catch. You might be able to get additional links added in at STS (Omega UK), you would need to call them and discuss it with someone like Simon (their service manager)
Here is a useful article I wrote on these very special watches
https://en.wikipedia.org/wiki/Omega_Marine_Chronometer
Fundamentally these are the same movement as the Omega Marine Chronometer but under calibre 1510, the movement was also used in a stainless steel example of your watch. In total there were 1000 made of which approximately 200 were solid gold, 50 of which have electric blue dials and 10 of which had solid gold dials.
You watch should be keeping time to approximately 1 second per month
Here is mine, this came through the forum from the son of the original owner, sold in 1975 it came with the original box and papers, sadly the bracelet was beyond salvage but it wear great on original sharkskin, not the most understated of watches but non the less a real beauty.
Mine was serviced at STS earlier this year, it wasn't the cheapest of jobs but their lapping machine and onsite gold smith returned the case to basically new and the watch genuinely isn accurate to 1 single second per month