Gerrit.
The two resources I have referred to are
Piper Super Cubs in Dutch Service - http://www.pipercubforum.com/dutch18.htm
and
USASC-USAAS-USAAC-USAAF-USAF Military Aircraft Serial Numbers--1908 to Present
Joe Baugher - http://www.joebaugher.com/usaf_serials/1954.html
Also the page for 1952.
Both of these agree with the following, excluding registrations not taken up (ntu).
R-138, 54-2428, PH-KNJ, PH-GRC, cn 18-3828.
R-133, 54-2423, G-BLTH, cn 18-3823. R-133 has yet to be added to the database.
Hope this helps.
Malcolm.