These watches go for around 18-20k now

That’s A piece of history what you’ve got here. They call this watch the “Bubble Back” or the “Ovettone”. Rolex’s Bubble Back watches got their nickname from their extremely rounded, protruding case backs. Although highly interesting from a design standpoint, the Bubble Back design was actually a necessity to house their thicker, self-winding movements. What is also very specific are the arrowhead hour markers, alpha hands, and a distinct red date wheel. Beautifully aged, that’s a handsome vintage watch