In-built rarity through "limited production runs" is one of the easiest ways to get burned. That rarity can be destroyed any time the manufacturer decides to cash in.
I'm a firm believer in letting the marketplace (that's people like you and me, not antique dealers or eBay traders) decide what is valuable and then, if I like it, I might buy one.
I own several instruments which are appreciating steadily in value, though none of them is 'investment grade'. I play them fairly regularly, don't worry too much about the threat of adding another scratch, and never need to worry that a 1957 Precision or a 1965 CAR Precision might start to lose value.