To the OP
This thread would be better served on the B&W forum, not here on the 35mm cameras forum.
So, what is the APX 100 you see around these days?
Agfaphoto APX 100 is the remains of a 2005 Agfa master roll that has been frozen. Last year, Lupus Imaging (who is the distributor, it doesn't make any actual products) sent the remaining master roll to be slit, spooled and finished. All the stock you see today when it is finished, that's it. No more APX 100 is available.
BTW, the reason you only see 35mm stock is due to the film base thickness is only suitable for that format.
"Silvermax is APX 100"
No sir, it isn't. Its formula is based on the APX 100, but it is new material as ADOX have said in this forum when it was introduced.