Personally, I wouldn't classify that as a cud. I don't see a break on the rim extending into the field. It just looks like a die chip at the tip of the "6". Chris
I sent a pic of this coin to Mr. Stevens at Cuds on Coins and he agrees with you, that this is not a cud. I made the assumption based upon others I have found.
It's all a matter of splitting hairs and deciding what you're going to call something. A die break, by definition, is when a piece of the die breaks off and falls away. A die chip, by definition, is when a small piece of the die breaks often falls away leaving a raised lump on the coin. So a die chip, technically is also a die break. A cud, by definition, is a die break that involves the edge of the die. What we have on the OP coin, is a die chip (die break) that involves the edge of the die. That matches the definition of a cud. So technically the OP coin is a cud, although a very minor one. Apparently minor enough the person running the codes on coins website, isn't willing to recognize it is one. But is not recognizing it does not change what it is. It is not a rim cud though. A rim cud is confined strictly to the rim and does not extend into the field. The cud the OP coin is confined to the top of the six and the field, and does not extend into the rim.