Seeing the pic brought a flood impressions. First, it is in immaculate condition for the age. Second, that the saddle is an obvious replacement and the bar tape was also probably replaced, to match the saddle. Finally, and most disturbing, it does not appear to be pre-1975 model.
I should have mentioned this. The saddle, handlebar tape, tires, and the white brake cable tubes are obviously new. But I do agree that, other than some minor scratches on the frame, and a bit of rust here and there on components, it is in quite great condition. I was very surprised when I discovered the bike was form the mid '70s!
We have a couple of known reference points for mid-1970s International based on surviving literature. The 1974 used the original graphics, a Maxy crankset and stem shifters. The 1976 had redesigned graphics, a Maxy II crankset and bar end shifters. Yours has the redesigned graphics and Maxy II, yet has stem shifters. Of course the shifters may have been replaced but it could also mean a 1975 model. It's obvious that it is not a 1974 model.
The component code does indicates August 1975. Most manufacturers started building for the new model year around September. Depending on the time lag in delivering the parts to the factory, it could be a very late 1975 model or a very early 1976 model, assuming the derailleur is OEM. Given the conditition of the bicycle, it probably is.
Interesting, this makes sense given the code on the derailleur, which I would assume is OEM given its age (although it too is in good condition, a little rusted but working, although in need of tuning, as it doesn't shift great). The additional info about the graphics is interesting...do you have sources, like a scan of the literature?
So how do I explain the serial number? Unfortunately, the database is currently down. I'd really like to review the data I have from this period. However, pending further investigation and evidence, there is the possibility that the serialization format actually changed during the 1975 year and/or that the frame was built in 1974 but went into a rework recycle for some quality issues that delayed it's being built up.
I'm really curious about this bicyle and the apparent discrepancies. It would be appreciated if you could check for other date codes. There should be codes on the back of the crankarms, back of the brake calipers, back of the front derailleur cage and bottom of the stem. There may also be one on the bottom of the seat post. TIA.
What I will do, when I get a chance, is grab some more pictures and as many serial numbers off the components/frame as I can. This is an awesome thread T-Mar, thanks!