Dirt-diggin-fool, You are right that: Experience shows that if the signal at the start, is eventually not commensurate with what the pinpointer is telling you, that , yes , it is too big to be a coin. Example: A soda can at 1 ft. might *sound* like a quarter @ 2 inches. Right ? Hence you KNOW something is wrong when you've got 4 or 6" out of the hole, and still not a peep on the pinpointer (yet your detector still shows dead-center in the middle of the hole). This usually means it's something bigger/deeper, hence not a coin.
But this struck me as SUCH AS EXAMPLE of a side-phenomenon of our age of dazzling detector improvements: Ever since the late 1970s and early 1980s, it has become easier and easier to "size up" and "TID" targets. This is GREAT for coin-hunting. You can sort of 2nd-guess size, depth, shape, and conductivity (if and when a bit of "cherry-picking" is in order for certain junky situations). This has made detecting a lot of fun.
But an un-intended side consequence to this, has been that a lot less caches are ever found nowadays. Contrast to if you ever study the finds of those with primitive lousy BFO and early all-metal TR (1960s to early 1970s), you see a lot more caches (albeit accidental) found in those days. Because BY THEIR VERY NATURE, they lacked sensitivity or tell-tale-audio that we have now. And while they may have struggled to get a coin to 4" deep, yet they beeped quite nicely on deep hub-cap signals. So back in those days, w/o "whistles and bells", more caches were dug. But today, we are spoiled and pass those durned hubcap and soda can signals (durned that junk anyhow).
Kind of ironic how less-able machines of yesteryear were actually the superior coin-hunters. The less sensitive they are to small objects (single coins), and less tell-tale audio to spoil you, then the more "hubcap and soda-can" sized objects you are forced to dig.
