Checking the "Hamilton Serial Numbers and Grades" on the Complete Guide, I noticed that 974 started in 1897, whereas 974L & 974P in 1911. What surprised me is that there still are runs of 974, without L or P after 1911. I do not know what is the difference between a 974 and a 974Lever Set or a 974Pendant Set: I was thinking that introducing Leve Set automatically made pendenant sets "P", but if so, how happens that there are "simple" 974 ?
Thankd a lot for your help

Mario, The 974 was only made in P and L types. The L & P reference would only be important when th "P" type appeared, I have no explanation why the price Guide continued to list some without the L or P after 1911. The price guide was just Guesswork as far as Hamilton manufacturing dates.

You need to look at the Gelson List at;

Hamilton Serial Number Listings Preserved by John F. Gelson

which in our Technical Library and Site Links is a well researched reference. Ehrhardt's last Hamilton book includes the Gelson list that shows the correct Hamilton production dates and model designations.

David, thanks a lot. This makes sensa, there are two versions, all clear (the third would have been "pin set", rather funny for Hamilton, isn't it?). I never used that part of the Guide, I normally check serials on Burgell's dB, so now I have a quite sounder base to work with.
It's always an enlightening pleasure reading you !
Take care