Original vintage 1970s Seiko 5 (Thong Sia) advertisement - only the advert in the first slide included.
 
Dimensions: 10 inches wide by 13 inches high.
 
The Seiko 5 automatic watch series was a wide and diverse line of automatic watches in the 1960s and 1970s, up to the current day.  During its early years, the most popular Seiko 5 line was its 70-meter diver watches; the line was aimed at “light” water sports that gained in widespread popularity during the late 1960’s and 1970’s – hence the 70-meter dive rating; however, these dive watches did not feature diving bezels.
 
Even today, Seiko's 5 Sports line continues to win plaudits - as noted recently in GQ Magazine, "Regardless of where a budding collector might be headed, the first question they all have is the same: Where do I start?"
 
"My answer is the Seiko 5 Sports line.  These watches check all the boxes: They’re affordable, distinctive, and, despite costing a fraction of what most mechanical sports watches do, are built to last.  The famed Japanese watchmaker launched the 5 Sports line in 1968, and revamped it in 2019 when it released watches...at prices that seem to be missing a zero."
 
"For the aspiring collector who has never owned a watch, the attractive price point of a 5 Sports may be all the convincing one needs.  And for the burgeoning horologist who already owns a timepiece or two, these watches come with the history, the quality, the sophisticated design, and the functionality that make them every bit as essential as any Swiss brand to a well-rounded collection."

As noted by Worn&Wound, Seiko’s marketing ads boasted about the 6106’s diving capability, that was “Proof," all the way down to a whopping 229 feet (!); other ads made the line seem like the choice for surfers.  Granted this makes for some shallow diving, but not in the era these debuted.  Regardless, it was a popular offering and affordable. 
 
Seiko made literally hundreds of Sports diver variations during this time period, with the Japanese manufactures’ Suwa and Dani factory seemingly in competition with one another to see which could devise the most compelling models.