an "effortless design" is the point. Large, stainless, sporty pilot case, large easy to read luminous numerals, basic-appearing dial and hands (though not nearly so basic in execution as you might expect), wonderful dial color. Sort of un-Patek, but...
but I would say they should be examined as closely as possible via loupe or macro photograph. But as we see it is tricky as not all hallmarks have the same crispness coming out the factory, and irrespective of any polish, this may vary by year of...
I think both of these pieces would fit you very well, figuratively in terms of your horological tastes and appreciation, and literally in terms of your wrist. You don't mention whether you would prefer the 5078P with white dial (enamel) or black dial...
The most reliable info I have heard is that 20-something steel L1's with white dials were produced, sold by various dealers around the world, mainly in Asia and Europe. 3 black dial steel L1's were produced, all ordered by Pisa Orologeria in Milan....
I don't think it is quite correct to say that these "vintage series" watches (such as this 5970J with brown dial) were produced for the London Exhibition, even though that is where they were first shown. Several were sold some years later. Or maybe 5...