Caliber

Hi, I'm new to IWC world... I have an IWC pocket watch: serial no.: 797907
On the movement it reads: 662253 H6
What does H6 mean? How do I know what is the caliber of my watch? How do I know the year of production? (I found on the internet that - accoring to the serial and movement no. - the production year should be 1915-1920, is it correct?
Thanks a lot!

Thank you very much for the information!

Thanks once again for your quick answer. I tried DateYourIWC and it raised one more question:
It says that the movement is from 1917, and the case from about 1923.
What does it mean? Is 1917 the date of actual production or the date when a certain type started to be produced? Did they use for the watch in 1923 a movement that was 6 years old, or does it mean that my watch is made of a case and a movement that originally did not come as a single product?
I hope my questions can be asked easily and thank you in advance for the answers...