xavier,
I went back to reread your post on your CJ-3A rebuild.
There is a book you may want to add to your library:
https://cj3a.info/book/index.htmlThere is a lot of detail in Bob's book. Also from the CJ3A Page:
https://www.cj3apage.com/index/Tech_Tips/dating_a_cj.htmWith info to date your jeep.
Some details I've read, there wasn't any factory stamping on the frame (don't know if it could've been done by overseas country). Also, the book has a table showing Serial Number details. Your stamp follows the early Serial Number prefix, "CJ-3A" before the serial number. If this is a 1953 model, then the Serial Number should start with prefix, "453-GB1" before the serial number.
However, that is a Belgium tag. Here is some information on the Wilford distributor company from that time frame on the CJ3B Page:
Jeeps in Belgium on CJ3B.info
Notice there on the example that they stamp the tag for a CJ3B the same, "CJ-3B" even though the serial number should show "453-GB2"
Is it possible that all Belgium imports were stamped how you see yours and the date stamp you see is accurate?
On that 3B article there is a link to the Belgium club on jeep heritage but it must have changed. You may already know the club there but just in case, here are links to the FB page and club website:
https://www.facebook.com/jeepclubbehttps://www.jeeper.be/content/page.aspThey may be able to help with historical information on your jeep.