As usual, the game continues with the Chinese camera manufacturer's "Fun with letters" game so it may be too early to know, even the link to the cam on Hikvision's own site is 404.
But I did find this gem on another forum ==>> here.
My vote for the "F" ? I say it has an SD card door with a reset button inside it.
1 line: DS-2CD1xxxx are value series
2 line: DS2CD2xxxx are pro series
3 line: DS2CD3xxxx are ultra series (Hikvision were previously calling these 'core solutions' or some such bollocks before they renamed the 3 line 'ultra' which is also confusing because previously the 4 & 6 line, then later the 5 and 7 line were the 'ultra' models