website
https://www.hdekker.info/registermap/MC.htm
gives some more information.
translation:
Registered with KLM on May 30th 1954
Conversion installed in 1955 (no date)
Deregistered May 6th 1963 (next registrations known
PJ-CVB, HP-485, N423AJ), The PJ-CVB registration is for the Dutch west indies.
The National Archive has an accident report for March 23rd 1956 (The name Convair 340 remained) with a Dutch Navy hawker seafury. Unfortunately because it involves a military plane the report is not public. December 13th 1956 is also mentioned. Not sure if that is a second incident or just the date of the publication date of the report.
The conversion to 340B or 440 includes a longer nose and rectangle engine exhausts instead of round ones. Diffcult to see on your photo.
see
KLM Hamburg
The color scheme of the whole fleet was changed in the early 60ies. That would confirm your limitation of pre 1960.