I purchased some of the J&C version of this film in 2004 when in America [10 rolls = red fire cracker paper wrapper] . I shot one roll and processed in rodinal with no problems and nice results. I returned to Australia and promptly froze and forgot the film. Most of my photography these days is 5x4 but I do enjoy my medium format so last year decided to check if my old Shanghai had any of the issues reported with newer film. The old 2004 film still processed very nicely with virtually no change in base fog. No print through or backing numbers. I ordered a 20 roll pack off ebay and it was a 2015 batch and this time sealed in a silver foil wrapper. I'm tight so shot a single roll and cut it into 3 segments and used 2 developers and 3 methods to see how the later film behaved.
[1] Rodinal substitute 1:50 5 minutes prewash - 15 minutes development 21c - Jobo
(there was a url link here which no longer exists)
[2] TEA developer 1:100 5 minutes prewash - 10 minutes development 21c - Jobo
2 gms Ascorbic acid
3 gms Pyro
.5 gms Phenidone
TEA to 50 mls
[3] Tea developer as above 1:250 agitate 60 seconds then stand for 60 minutes - no prewash
Satisfied the 2015 batch is fine I got a further 10 rolls and this batch is 2016. Again silver foil and tested the same.
Film is close to box speed, I rate it at 80 iso and use a Spectra Incident meter.
Tonality is good, sharpness and grain are good and the film over a span of 10 years prints the same. The film stains beautifully with a Pyro developer.
Overall a good general film something like the results from Plus X and similar in ways to APX 100 - I said similar not the same

I've compared both as I still have 40 rolls APX 100
I haven't experienced the circles and numbers on the developed film.