That Zeiss Ikonta Question

1950 seems to be the date of the factory shutter flash synch for Ikonta &
Super Ikontas.

I got a great, clear reprint, "IKONA & Super-Ikonta Guide" by "The Camera
Guide", 1952. I haven't finished it yet, but it does list just which models
had shutters with flash synch. Prontor, Compur and Compur Rapid shutters for
the Ikonta and Super Ikontas since 1950 were internally synchronized for
flash, however the flash delay was fixed at X so one had to use shutter
speeds to accomodate the flashbulb's rise time. This means typically 1/25th
of a second for most bulbs other than the Speed Midget types (which are
quite rare today.)

There were some made with The Speed Synchronized Prontor SV shutter which
added a synchro delay options of 0, 5 to 24 milli-seconds via a dial with X,
F, M settings to better accomodate various bulb rise-times.

Interesting find - some Ikontas were designed to accomodate 620 spools as
well as 120 spools. There was also a model that used 616 rollfilm which gave
a negative of 2.25 X 4.25".

Finally, for those confused by the two red windows in the back - use the
window on the LEFT. Unless you have an adapter to 645.