Casio SF-4000 Digital Diary Organizer Calculator Calendar Made in Japan WORKING | eBay
VTG Casio Digital Diary SF- 4000 w/Manual Good Condition Org. Owner Not Tested | eBay
Casio SF-4000 Digital Diary - Etsy
Found this old gem today... Vintage Casio SF-4000 'digital diary' from 1988. Featuring a whole 31,902 characters of battery backed storage. : r/retrobattlestations