Becker 1480 won't physically fit in my w124 dash
 

I just acquired a Becker 1480 head unit.
It has the period look I am looking for in my 1992 W124.
I wanted to test fit it the dash but I was shocked to find that it won't physically fit in the slot!:eek:
It just starts in and it is a super tight fit and just won't go any further.
I'm quite puzzled.
What could be happening?
Am I missing something obvious?