In Europe, I met a collector last year who had (unbelievable as it might
seem) about a dozen vintage Portugiesers and was quite familiar
with them. The earliest ones that Cal. 74 movements, but were from
the early 1940s. Later ones had Cal. 98s (by the way, the 9828
differs from the 982 by having the special engraving on the back).
The papers that came with my Jubilee Portugieser also refer to the first Portugieser movements having a Cal. 74.
I was told by a reliable source that these watches were made in various
small lots over the years and that less than 600 in total were
made. I suspect that IWC made them based upon what they had around
or what the buyer (distributor really) ordered. I've seen many
different dial variations, including ones like Mk11 posted recently,
which differs from the ones you've shown and those depicted here),
and also some crown variations.
MF