I'm still looking into the history of the Schrade and there is a lot to dig through since this Company goes all the way back to roots in the Ulster Knife Co. of Ellenville..1870's...to Schrade Cutlery Co. founded in Walden...1904...to Imperial Knife Co.in Providence. As noted by the 1904 date...Schrade celebrated it's 100 years anniversary, just before closing it's doors in 2004.
They made some Anniversary knives commemorative of that, and made a practice over the years making knives with "collector's" in mind..as well as various authorized editions..inwhich they were festidious to preserve the integrity of these models with marking them as such. I don't know all the markings..as I'm still learning myself. On your knife though I think it would say Heritage on the tang stamp. I've also seen Schrade Ltd. How ever they called it, you'll have no question to an authorized version...it will be marked. Serial numbers were not a sign of special or premium I don't think. I own many LB8's and 171UH's that are numbered...and these are just regular run production knives.
Also in your question...are they "better built." (Heritage series) I really don't think so. They, I think maintained a very high standard of quality in all models. I just think a Heritage series, Limited edition, Special edition, Commemorative edition were models made separate from the production run for various reasons, not made "better." Take Special edition for instance....they took some Old Timers and placed Cabella's sheilds on, in place of OldTimer sheilds...a special run of knives for Cabella's. I think they also made some special run Harley Davidson too, and I'm sure many more as well.
Any way..I don't think they were "better" made, more so than maybe done up different.
Some were made with real bone handles as you say. This Company is older than the age of plastic too keep in mind. I like my Staglon or Derlin handles. I like real bone too..if I can get them, but I worry more about breaking or cracking them. Schrade used shinbone of beef cattle. I am partial to stag or deer antler myself. I'm trying to fit a nice deer antler now to one of my 171UH.
Schrade used 2 kinds of steels. My personal favorite is the AISI 1095 high carbon steel. Depends on what you are using it for..carbon steel discolors when cutting meat, fruit and will rust easier.
The other is AISI 440A stainless steel...and this will be marked on the tang Schrade+.
Special run knives over production run knives also come with a nicer presentation box...incase you intend to collect the knife, and then there is also the question of authorized sheaths. Factory authorized versions of any model will carry certain identification. Knives from factory 2nd stores or "off production" makers....or maybe even some last ditch churn 'em out knives in Schrades final days will be any ones guess...and not intended for collecting..just using and enjoying for what they are...just don't get ripped off buying them.
I just spoke with Robert Clemente about much of this. He is extremely knowledgable and has a book on Schrade knives...with a new revised edition coming out soon. I'm anxiously waiting for it myself.
Give Robert an e-mail and he can help you far more, and tell you about his book. He answer's e-mails right away, and is very considerate.
clemente@charter.net