W.ab is not the designation of these tubes.
They were manufactured or selected for the former "Luftwaffe" (German Air Force). W.ab stands probably for "Werksabnahme" or "Accepted work for the Army". There is no numbering for W.ab.
More information about these examination stamps is given in this link. If we know more about this particular examination number you will find a forum article below.
We try to show here all different tubes with this paricular W.ab-number. Each picture legend should give information about the actual tube type plus all other markings on that particular tube. We would like to show only one picture for each tube designation if all other markings are the same (incl. Date).
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