Hi Hairspringharry,
the Movement of your watch is a IWC Calibre 852 produced in 1952. Cal 852 is
an Pellaton automatic movement of 29mm diameter, was produced in 49200 pcs and
was produced from 1952 to 1958. Your movement has a pretty low serialnumber
for a Cal. 852, the first serial Number used for 852 movements is 127401 that
means it comes from the fourth batch of 600pcs produced.
The dial on your watch doesnt show the Automatic designation, which should be
there, that most probably means that the dial has been replaced by one that
was intended to be used for a manual wind center second movement like Calibre
89. The Cal. 89 and the Cal. 85x family share the same position of the dial
feet, which makes the dials interchangeable.
From the pictures you show, the case is not a monocoque but a normal case
witha a middle part where the movement is mounted and a case back which can be
removed. All monocoque cases come with a split crown assembly.
Nice early automatic watch anyhow,
-br
Cromagnonman
P.s. take care on your hairsprings - Harry