The 61GS is what Suwa Seikosha built with everything it learned racing the Swiss: through the 1960s Seiko's factories entered the Neuchatel and Geneva observatory competitions, climbing the standings year over year until quartz ended the contest, and the adjustment skills from that program went into a production watch beating at 36,000 vibrations per hour. The hi-beat 6145 with date and 6146 with day-date arrived at the end of the 1960s, sources splitting the introduction between 1967 and 1968, and ran to about 1975, the longest and most varied line of the vintage era.
The variety is the collecting map: above the standard watches sat Special grades with calibers 6155 and 6156, and above those the VFA, Very Fine Adjusted, watches at 6185 and 6186, hand-adjusted to tolerances Grand Seiko would not match again for decades. Early dials say Grand Seiko where later ones say Hi-Beat 36000, one more dating instrument in a family full of them.
The vintage blue chip with a built-in ladder: standard, Special, VFA. Each rung multiplies both the price and the incentive to fake the rung, and VFA claims deserve the burden of proof that any trophy claim carries.
Production windows and specifications compiled from documented collector references and period catalogs, cross-checked across independent sources; manufacturer records for this era are approximate by Seiko's own account.