I have never sold a Parker for less than I paid. I have never had to send a Parker to a gunsmith. My "investment template" is as follows:
(1) Less is more. A collection should not exceed 10 shooters plus, maybe, 10 wallhangers, if you collect both. No one can really grasp more than 10 guns at one viewing session. More than 20 representative examples is an accumulation.
(2) Know your wants and needs so you don't go off half-cocked. There are plenty of good-condition shooting-man's Parkers always for sale, but if you are in it for, say, an all-original high-condition "Parker Story" grade CH(E) gun in any gauge (especially one the small bores), you better do your homework. I have had my feelers out since 1997 for a late-model (post-1925) AH (no ejectors, please) 12-bore, 28- or 30-inch, with a straight grip in 70% case colors or above with all-original condition, but no luck. Picking and choosing among the scarce guns with flur de lis drop points can take time, or compromises...
(3) Be a cash buyer; use cash as a club to not pay too much. You cannot go to a gun show and offer $5,000 for a gun with a $7,500 price and expect the seller to take an out-of-state check.
(4) Buy only original-condition shooters you absolutely love (high original condition is closer to new); a gun advertised as "New by DelGrego" or "New by Turnbull" is not new, any more so than a car is "New by MAACO" by virtue of having a new coat of paint. (These people are friends of mine and do good restoration work, but a gun restored because it needs it is not new by any common understanding of the word.)
(6) Compromise on grade and maybe slightly less case colors in original condition, but do not buy a gun in anticipation of flipping it when you find something better. Buy only to own for a long time. It is always easy to buy, but more difficult to sell, and when it is time to sell, high original condition trumps all else. Winchester rifles and Colt revolvers may bring big prices because of storied ownership, but Parkers that have brought high prices because of ownership provenance can be counted on the fingers of one thumb.
(7) I have always preferred to buy from among the "usual suspects," being well-known dealers. I have never had a negative experience with these people. Those who troll the Internet auctions should add something as an "insurance reserve" to the price they pay to make up for the potential hassle and risk. In the final analysis, almost all the truly "investment" quality Parkers are well-owned and will sell to or through first rate dealers or at one of the top auction houses. These people make a living moving good guns and they are due their commissions...
(8) From strictly a Parker gun standpoint, I expect the "usual suspects" will have sufficient inventory at the Pintail Point Vintage Cup next weekend to satisfy most wants and needs. Jim Julia has an auction a week later (Oct.6) with at least 44 Parkers cataloged. Forty-four is a magic number for me; when I started to get interested in earnest in 1993 I called HC for his list by mail, and when I got it there were 44 Parkers on it...I called in disbelief and asked if he really had so many on hand, and he said that he was always turning inventory, but, yes, he had at least that many. I loaded my Volvo S/W with my wife and Choc. Lab and drove 1,100 miles to Terrel TX...and now I think I know something about the "Old Reliable." Follow my advice and your purchased guns (Parkers or other well-respected makers) will be an "investment." EDM
