I have an older steel frame (could not even attempt to guess what year it was made). It has a reynolds 853 sticker on it and it weighs approximately 6.2 pounds (frame and fork). The guy that I got the frame from told me that it was a Lemond frame, but it is 56cm and, from what I can tell, Lemond seems to make frames in odd numbered sizes. I cannot find any rust on the frame and it appears to be in good shape.

Now, my question: Is this frame worth building on or should I try to buy a newer road bike? I already have a full tiagra group (minus the bottom bracket), wheels, and a seat. I have been mountain biking for years, but I've never really dealt with the maintenance of a bike.

I have already taken this frame to two of my local bike stores and the employees did not seem to know what was going on, so, as crazy as it may sound, I'm turning to the internet for advice.

Since you already have most of the parts already, why not try it? The key to your remaining parts is to find a donor bike, and then "borrow" the parts you need. You can spend a lot of money buying your remaining parts one at a time. In that case, you are just better off finding a complete bike (used of course) that you like and fits well.

There's no reason to doubt that it's a Lemond frame, here's why : the Wt. is typical
As a tig'd 853 frame outs it as a late '90s or beyond, all the same dimensions.
Earlier ones 853 and otherwise were lugged, it those which had even sizes.
You've meas. it incorrectly perhaps. A lugged would meas. 56 CT by 56.5 or so TT
55cm, later frames were 55CT with long TTs, 57(or so) TTs always meas. CC
So do try to meas. it again. I've meas. these myself, owned 'em and recall data.
The point is that he nor others focused on precise meas. just to be handy.
One Al. frame I own and rec. ck'd out meas. slightly larger than it's 53cm ought to.
The paint looks unfamiliar but the type of paint appeared as LeMonds right off.
Knowing all that's been available (within reason), in tig'd 853, I can't possible come
up with a more rational idea. LeMond has a data base, if nothing else.
I could of course, stab at a comment.. "generic" or such but that'd be silly.
Shops don't care or know enough to venture a guess, they've no stake in it.
When I ventured into shops that had Trek which owed LeMond, it was as if I
was talkin' about a Fuji... "different division Mister, sorry" so much for that.....
Do the ID # thing VIA the Site, it comes-up as the first entry.

- there is an extremely high likelihood that this is a Lemond frame (the CM count is all about one's tape measure and where they count the C-C from; and Lemond bikes at the early 90s were practically all built with 853s. Not many other 853s out there...).
- Tiagra would probably insult that frame (check the frame spacing for fit, btw, get a 8sp Dura Ace gruppo and will make you happier) and, yes, this frame is extremely worthy of building (unless you weigh more than 200 lbs - 853 was spec'd for 150 lb load, but you can mitigate with the right wheels and 25 inch clinchers)
- Get a different bike shop ASAP. If they do not know those frames, it is very likely that they do not know other things as well...

old and new, your post is pretty damn near unreadable.

Nice frame. RIde it!