In my case ( I have a thread going about a couple of Schon cues) I have looked through all the online catalogs and just must have missed one and didn't find the other anywhere. I also looked through current and completed auctions on Ebay and other dealers to see if I would get lucky and find them there.
One cue I was trying to find out about was a Viking. They have extensive catalogs online and It was not in any of them. I emailed a picture of it to Viking and it turned out that it was a cue that was not offered in a catalog and was only offered in online sales.
In the end, not every cue ever made was in a catalog and often not all the companies catalogs are archived. Not all catalogs are online. Not all cues are still marked, some markings have worn off.
I have a Huebler cue I bought in a local shop back in the early 90's that I have never seen in a catalog
I have 46 cues to research and have figured out about 20 of them so far.
In my case, an original retail value or educated guess is good enough and usually the MSRP is easiest to determine, often from a catalog listing.
As for why I asked about the Schon cues was clearly stated in the original post.
My Google-fu is pretty good so I am usually really stumped if I ask about something in a forum.