My opinion: Parkers are still failing to perform...
Using a Parker afield or at the traps is like fly fishing with bamboo, strictly a personal preference and a connection to the past. Emotion. A more rational gun (or tool) for reducing birds to possession would be a Remington 870, cheap, reliable, disposable, and more shots. Condition is nothing. Destry used to joke that our duck hunting guides in Dalacroix LA would just toss their 870s in the back of their truck with a few fist-fulls of sand and let them slide around on the way home to get rid of the rust. Different strokes! They admired our Parkers but wouldn't own one for free. They wanted a "tool" to kill ducks.
As to condition, condition is everything but slightly subject to availability. If you want a common VH(E) 12-bore the pecking order is pretty clear and the Blue Book somewhat instructive. But scarcity sometimes trumps outright condition, especially in the early lifter guns; in other words, don't hold out for a high condition T-Latch or a 16- or 20-bore lifter gun.
As to buying Parkers as an investment, I think selected stocks blue chip stocks are the better deal now. ATT at today's price pays a 7.2% dividend, it's making money, and just raised the dividend. The market IMHO is over-sold and panic sellers are not rational. It takes some guts to buy low when everyone is selling, but in retrospect is the best way to buy. Parkers are pretty high now and might go higher, but they don't pay any dividend unless you shoot them, and if you shoot them they aren't "investment" grade. EDM