Help required with recognition of IWC wristwatch if possible please

I have just recently acquired this IWC wristwatch, tho it looks quite a nice piece I have since acquiring it begun to have my doubts to it being a genuine IWC or not, it measures 45mm across the case including the winding button,the backcover is clear glass so as to view the movement, it has a serial number of 690631, the case is stainless steel,winding button looks to be plated on close viewing, the small offset seconds is situated at 9 oclock.
I would be most pleased for any assistance from members or the Moderator should you have any information regarding this model.
I have a IWC vintage wrist watch these many years and when first purchased in the early 1980s I actually sent it back to Schaffhausen in those days for servicing their after sales service was supreme, and the watch is still as accurate today and has the looks to go with it.
Many Thanks up front for looking at this posting.

hmmm. first interesting point is I didn't realize one could start a post in Archives, lol.

second interesting point is the provenance of this watch, and thanks for posting Chemawa. right off a question to the experts of the forum from an amateur: could this be one of the 304 pieces of the ref 325 Portugeisers ?

The dial design looks different from previous ref 325s I have seen. The movement design however looks real to me, but this is just my opinion, compared against pics from Michael's excellent website. I also quote:
"[b]Calibre 73 and 74 pocket watches often are easily identifiable from the dial and case, without even viewing the distinctive finger bridge movement. Frequently as products of the 1920s, they often had Art Deco style dials with stylized numerals. The relatively thin cases often had striped engravings or Grecian motifs on the bezel area, sometimes filled with enamel.

Being relatively small for a full-sized pocket watch movement, the Calibre 74 was also used in IWC's first wristwatch that used a pocket watch movement, the famous Portuguese wristwatch (reference 325). 304 examples were used in the Portuguese wristwatches between 1939 and 1952.[/b]"

DateYourIWC by case and movement number (I prefer the applet version at the bottom), created by Marco Schönenberger, says:
Movement number 690,631
Case number 690,631
Main findings: Summary
The movement is a LÈp. calibre 73, dating from the year 1918.
Valid entry in "Index of Movement Numbers"
1918 690,101-691,300 Lép. c. 73 - 17lig. H 4

This article by Marco Schönenberger states:
gen. ref. cal. name/ Production
1. 325 74 Original Portuguese (Ur-Portugieser)
1939 - 1944 (a few even later)
around 304 pieces known

A marriage watch ...of little value / interest ....hope you din't pay too much for it

Many thanks to you Michael, Shing and Ivan for your comments re this enquiry and confirming my doubts.
Regards Terry