One thing you can try is to run unidasm on it and see if it looks like valid 6502 code:

Code
./unidasm -arch m6502 Dumpling-GX-ROM-2732.BIN -basepc c800

c800-cfff is a 2k rom region where expansion card roms will appear so if you want to see if the next 2k bank will slot in

Code
./unidasm -arch m6502 Dumpling-GX-ROM-2732.BIN -basepc c800 -skip 0x800

and one thing I like to do is to run a little lua program to see if there's any strings lurking with the high bit set:

Code
f = io.open("Dumpling-GX-ROM-2732.BIN")  a=f:read("*a") print(a:len()) for i=0,a:len()-1 do c = a:byte(i+1) if (i%64 == 0) then print() io.write(string.format("%4x",i)..": ") end c = c % 128 if c>=32 and c<=126 then io.write(string.char(c)) else io.write(".") end if c==0x1b then io.write("ESC") end end print()

one liner expanded to multiple lines:

Code
f = io.open("Dumpling-GX-ROM-2732.BIN")  
a=f:read("*a") 
print(a:len()) 
for i=0,a:len()-1 do 
  c = a:byte(i+1) 
  if (i%64 == 0) then print() io.write(string.format("%4x",i)..": ") end 
  c = c % 128 
  if c>=32 and c<=126 then io.write(string.char(c)) else io.write(".") end 
  if c==0x1b then io.write("ESC") end 
end 
print()