Rolex ref 6309 Thunderbird Bubbleback Datejust Yellow gold (from 1955)

Previously I have bought a 18k Rose gold Rolex ref 6309 Thunderbird Bubbleback Datejust Rose in May 2022. My focus is to grow the so called Big Bubbleback series as the Rolex 6309 is using the semi Bubbleback movement.

After several years, I have finally come across a 18k 6309 in yellow gold. Besides the difference in colour of the gold, the bezel is also different from the rose gold crisscross “clous de Paris” design engine turned bezel design.

Timeline of Turn-O-Graphs from the internet:

source https://www.reddit.com/r/rolex/comments/1pf3aud/cool_rolex_of_the_day_2895_6309_turnograph_with/

• 1952-1953: Ref. 6202 debuts, the first Turn-O-Graph. While the steel model resembles the soon-to-be-released Submariner, the two-tone model has a gold bezel that most associate with the later "Thunderbird" models.
• 1953-1956: Ref. 6309 ditches the Sub-style bezel in favor of the gold "Thunderbird" one. Full gold is now an option, as is a left-hand crown.
• 1956-1959: Ref. 6609 is "basically the same as 6309 but with updated 1065 movement (based on the cal. 1030 but with date)" This is the model that sparked the nickname "Thunderbird" because Rolex famously gifted some to the USAF Thunderbirds.
• 1957: Ref. 6602, a rare Datejust model called the "Transcontinental," is the only Rolex ever made with a 12-hour rotating bezel afaik. Someone posted this one here years ago; I assumed it was fake at first. Sotheby's calls it a "6602/6609" but 6602 is what's actually engraved on the case in every known instance. Here's a TRF thread about another example.
• 1959-1976: Ref. 1625 gets a movement upgrade to the Caliber 1500 series. At first it sports a 1565 movement, with 26 jewels vibrating at 5 beats per second. Starting in 1965, the 25-jewel 1575 movement ups the rate to 5.5 beats per second while increasing the power reserve from 42 to 48 hours.
• 1977-1987: Ref. 16250/16253/16258 gets a movement upgrade to Caliber 3035, now vibrating at 8 beats per second like modern Rolexes do.
• 1988 - 2003: Ref. 16263/16264 gets upgraded to a sapphire crystal and Caliber 3135 movement. No more full gold models.
• 2004-2011: Ref. 116261/116263/116264 gets a more modern case, new bezel design, and Caliber 3135. Rose gold + steel is a new option. Small numbers of a special edition with a green seconds handmysteriously hit Japan in 2011, and a few European AD's a couple years later (though for some reason they have 2005 serial numbers).