Seiko; A Calculator Quartz Wristwatch, C153-5007, numbered "834230, on a strap, in a Seiko box.
Seiko C153-5010 – My Retro Watches
Seiko - Vintage Digital Calculator Watch with pen - - Catawiki
Seiko C153-5007 Black Vintage Digital Calculator LCD Quartz Watch - YouTube
birthyearwatches.com - 1977 Seiko C153-5009 Calculator watch. Can you see what I did there? #seikolover #seikocollector #seiko #1977 #birthyearwatch | Facebook
For Sale - 1978 Seiko C153-5007 Calculator Watch - SOLD | The Watch Site
SEIKO] C153-5007 1978 Calculator Watch. My only “smart watch”... : r/Watches