Look at this little guy I found last night in my unidentified hoard I've been going through. I have identified this as the 1930 Mexican 5 Centavos small square 0 type, which I'm pretty excited about and didn't expect to find. Do you agree? - and - I'm hoping for VF grading, but what do you think? - K
A better photo of the "0" would help. The "small" 0 is more square than round, Hard to tell from your photo. I hope your are right. Grade IMO is F/VG
I'm unfamiliar with the variety, but agree with @sonlarson that the grade is VG+. I would apply some Vaseline to the coin, then gently remove it with some soft cloth (fabric like from an old T-shirt is good). By gently rubbing (not scrubbing) the Vaselined coin, you can probably remove some if not all of that surface grime and improve the coin's appearance without altering its natural color. Mineral oil will work as well as Vaseline, but I've found it to be messier since it's more liquid and runnier.
