I played the Professional 100 back in the 90s. Loved that ball.

Yes, I have seen and probably played all of them. HP's are all older second-tier balls much like today's Tour Soft. The Professional was a top-tier ball but only was around for one generation. It was a transition ball after Tour Balata and before ProV1. It has a wound inner like balata balls but a urethane cover like ProV1. As for value, there really isn't much of a market for them unless you found some private collector looking for one to fill out a missing spot in their collection. BTW, thanks for calling them "very old" as I think of feathery and gutta-percha balls as very old. :) Time flies when you are having fun.

They pre-date 2001 when the Pro-V was introduced. The 100 was the higher compression version, the other was the “90”.

No retail value. Not sure they are worth much more than a dollar as a collectible. Only if it can be attached to an event, like one won by Davis Love, III.

I remember those but can't tell you much else. Probably aren't worth anything to say sell

static.wikia.nocookie.net/930b88bb-2dfc-427b-8966-0259c1539ead
Those are names I’ve not heard in a great many years! Not really worth anything aside from driving range fodder on the public side, but a great reminder of what cutting edge technology used to be.

The Professional 100 was one of the top of the line balls that Titleist produced prior to the Pro-V1's. Similar interior to the balata balls but with a harder cover to improve durability and distance. The HP's, both the HP Tour and the HP3 Performance, were similar to the position of the AVX and the Velocity these days in the lineup. These were from the '90s if I recall correctly.
These earlier posts on the TT Forum may help you:
www.titleist.com/.../evolution-of-titleist-golf-balls-remember-these
www.titleist.com/.../list-of-old-titleist-ball-models

I played the 100 compression professional for many years, but have never heard of the HP.

I'm trying to get them to bring back the Prov1left dot!!

I had my only hole in one with an HP2 Tour back in 1996. As others have said, it was a mid-range ball from Titleist that had a little sound and playability to it. Professional was a great ball, but pricy for its time, and being wound, you could put a "smile" in it if you caught it thin, similar to a balata. That went away when the Pro V1 came out.

I played them all and still have 6 Professionals in my old Jones bag with persimmon woods and forged blades sitting im my office. Someday maybe I'll take the whole set out for a spin... but its been since the 1980s!!!