Well Greybeard, i am afraid that no matter how accurate your worded description it's not really possible to give you any useful feedback without detailed images. Even then we are limited as holding a keris in hand can reveal aspects of it that photos do not, but at least with photos we can get an idea of what we are talking about. Perhaps you have a friend with a better computer that would allow you to upload.
What do you mean exactly when you ask if it is possible that the keris was "used" during WWII? Do you mean as a weapon of war? If so i would think that highly doubtful. By this time the keris didn't see too much use as a physical weapon anymore. As for the execution story, the keris panjang is generally consider to be an execution keris, though it was much more a matter of status than a blade used for regular executions. In other words, if you carried such a keris it generally meant that you had the authority to perform execution, not you you actually did it. It has a very long, slender, usually straight blade. The exection done with these keris was performed by driving the blade downward through the top of the shoulder into the heart while the arms of the condemned were held out-stretched. I do not know when this type of execution was last performed or if it is possible that such exections took place as late as WWII. Perhaps someone else has more information. It does seem from your description that your keris is not a keris panjang.