Yeap a song produced and performed by R. Kelly! I always remember this part of the lyric..."I believe I can fly, I believe I can touch the sky....." The very moment you believe, the sky is the limit.... Sky is the main theme here as I am talking about a vintage pilot watch. Seiko Sliderule aka Calculator aka Pilot ref. 6138-7000. Sliderule is one of the rarest variant of 6138 family and among the most expensive vintage seiko chronograph.
I just received this watch from the Philipine... it appears that everything is in good condition and is in original state apart from the bracelet. This watch shared the same engine with Seiko Bullhead, Speedtimer, UFO which is the 6138. 6138 is evolved from the Seiko 6139 a single register chronograph movement that was introduced in 1969.
There are two variants of 6138, namely 6138A (21 jewels) and 6138B (23 jewels). This automatic seiko in-house movement is beating at 21,600 bph and it can be handwound. This double register chronograph was introduced in 1970 with feature of quickset day and date.
The main attraction for this watch is its sliderule bezel that can be used for calculating vital figures for aviation navigation. Wait until I am qualify to fly an airbus A380 then I can tell you how this is operated.... Another mystery for me to find up is my watch movement stated 6138B and 21 jewels....
Anyhow, is never a bad choice to grab a hold of 6138 as it is one of the world's first automatic integrated chronograph movements. It is at least as good and as reliable as the Swiss manufactured cal. 11 and El-Primero movements but at a fraction of their price.
My sliderule is currently under quarantine. Wait until it is fully serviced, I will try to take a better shot of it.