As I have now been collecting Mexican coins now for around 10 years - seriously - I still see on rare occasions some oddities in these Chihuahua casts. Some past oddities have been:
1. Seeing mostly 1811 and one or two 1812 without any edge markings. Mike Dunnigan simply explained these were real and there was no concerns he had seen some himself (not often) with no markings on the "third side"). Simply human error in the process of applying edge markings on these crude types.
2. At a past NYITL in New York City at Aureo & Calico's table I have seen a Chihuahua cast with two "T" marks instead of the T and pillar of Hercules marks for regal confirmation. Another oddity. No concerns.
Here is a third oddity I just picked up although I did not purchase or own #2 above - this is an 1813 Cast Chihuahua but if you look at the images it has what appears as an off-center die struck marking across DEI and then creating more of a die break impression below GRATIA running to the bottom of the bust just at that STOP after the date. What is unusual also is this impression side (right obverse area - see pics) has a thickness measurement of 3.0 mm and the left side 2.5 mm or a 0.5 mm differential. Yes - the impressed side is THICKER. I have never seen this occurrence on any Chihuahua 8R cast before - additionally if this was not enough look at the corresponding reverse side
where we see these effects where it obliterates out the lower right pillar and also has it taking out the bottoms of 8R.
I remember something similar although not the case here where the late Bill Anton confirmed with me and few people could confirm this in the counterfeit English/Irish halfpence George II area where ~ 50% of all coins were cast which is common knowledge to the experts although very few appeared struck on cast planchets. Although here the legends were sharp but the planchets had rim burrs and potholes so the legends were CRISP but the planchets or blanks were cast. We call these oddities struck cast 1/2d's. Anyway ...
This is not the case here as the legends are mushy, the appearance of these legends are cast like and this blank is cast (i.e., pinholes everywhere) but what is causing this planchet to deform by 0.5 mm and to have this type of die cutter or striking mark?
Weird & Unusual. I tilted the photos 90* to give the viewer a better view of this phenomenon.