Your boiler is definitly a 551 and the front you have WILL NOT fit.
Only suitable fire fronts are:
Bermuda S
GC No. 32-077-12
Bermuda C
GC No. 32-077-11
Bermuda W
GC No. 32-077-09
Bermuda PW
GC No. 32-077-08
Bermuda LFE
GC No. 32-077-10
Only suitable fire fronts are:
Bermuda S
GC No. 32-077-12
Bermuda C
GC No. 32-077-11
Bermuda W
GC No. 32-077-09
Bermuda PW
GC No. 32-077-08
Bermuda LFE
GC No. 32-077-10