The file vc-20-diag.324173-01.bin was read out of a TI 2532 Eprom, the
label to that Eprom says
                                                                                
324173-01
VC 20 DIAG
                                                                                
The Eprom was soldered in, on a PCB with Fab.No 324.171-01. The PCB seems
to be prepared to carry more stuff: 1K of memory is also located on the
cart, but there seems to be an option for 3K and another 4K Eprom. A bunch
of jumpers seems to make 4K/8K/16K cartridges on that PCB.
                                                                                
The cartridge itself is labelled
                                                                                
DIAGNOSTIC-TEST
VIC 20/VC 20
324159-01
                                                                                
The cartridge is brown plastic. Of course, there are some diagnostic plugs
in the set, but I won't have the complete set (the IEC port connector is
missing, I only have open wires on that end).