SoCaled 

I have a Trek I could use some help identifying.
Serial number is very confusing to me, based on other Trek numbers I am familiar with.

not my best set of pictures sorry about that, tried to get out of the sun, went a little too shady

Serial B?8C10

B?8C10 - not a trek format i know

Hobbiano 

I'm going to guess it's an early 412.

CO_Hoya 

Maybe a TX200/300? See previous thread here.

Hobbiano 

It could be. I'm not very familiar with those. It does look like it's probably got the original components on it. Does the crank look like it's swaged? I have an '81 or '82 412 and it is similarly equipped. But it has top tube cable guides. The tx200 in the linked thread has steel rims and a hex head seatpost bolt, and bolt on rear wheel.

CO_Hoya 

it’s the S/N that’s confusing me. It doesn’t seem to match standard Trek format (per the archived Vintage Trek page) but seems closest to a TX200, circa 1978.

Just a wild guess on my part, for sure.

Hobbiano 

This is from the '81 catalog:

SoCaled 

That's where I was starting to go based on a site that had some info from the defunct trek site
Serial B?8C10
Assuming that the first number is missing:
then B is TX200 - 8 would be for 78' - C would be March - and 10 would be 10th bike?

Hobbiano 

I have to agree with you that looks like a TX200 format S/N. I'm just guessing too.
I didn't think the question mark was for a missing number in that place but was questioning if the B was a B. Referring to the picture of the S/N, the characters seem to get lighter toward the left.

SoCaled 

The crank appears to be dated 79'? which seems to mess up a 78' TX as an option if crank is original
That said:
"According to the brochures, Trek did not make 41X and 61X bikes or frames during 76, 77, 78, and 79 and also not in 83, 84, 85, 86, 87, 88, or 89. These serial numbers apparently do not follow the year convention used for other Trek models. It is likely these frames, SNs beginning with M or N (Models 41x and 61X), were contracted out or were made in a separate Trek facility, and were given the old serial number form so as not to interfere with the sequential numbers being assigned by Trek in their main shop, which began in late 1980."

Hobbiano 

SoCaled The vintage trek site does say the serial # format should be L N L N L N N, seven characters, where L is a letter & N is a number. Maybe what you have is ? ? L N L N N, or ? ? B 8 C 1 0, where the first letter and first number are too light to read. Something made in Feb. 1978. Now if the number before the B was a 4, that would indicate a 24" frame size, which seems about the size of yours. Look closely. Do you see a 4 before the B?

AdventureManCO 

The transition from the screwed in headbadge to the sticker'd on headbadge...that was around 1980-ish? I'm probably wrong but I'm wondering if that may help identify OP's bike.

AdventureManCO 

While I can't confirm, this is what I think as well, 1980-1982. Someone who knows Trek colors and features better than me might be able to confirm.

SoCaled 

Nothing at all visible before the B, not even slight marks. Another thread mentioned the other (not part of the serial number) letter stamp being a maker stamp referencing the builder? There is the larger "S" on the BB. Then on the section of the BB that goes to the seat stays there looks to be a "J"

unterhausen

Unless that's a replacement headbadge on OP's bike, I can confirm that it's not a '78. And it would have holes inside the head tube if they somehow got ahold of a newer headbadge.
That's how I know if there is some possibility that I built it.

sd5782 

I have what I believe is an 82 412. I think this may be an earlier version as already mentioned. The 82 has the braze on rear brake cable guides. Lots of other things resemble the 412 in the frame. The Dia Compe 500 brakes and lack of drop out adjusters match with 412. The VX front derailleur matches. Mine came with a VXs rear. I can’t tell what this has. The 82 had an SR custom 42/52 crank vs this SR apex. The freewheel looks to be the same because I see that strange gear spacing as on my 82 which goes something like 14-16-19-23-27-30. I didn’t understand that 23-27-30 setup. I’m betting maybe 1980 or 81.

Hobbiano 

SoCaled Compare the details of you frame to this one: John's Bicycle Restorations: Ruben's 1980 Trek 412 Restoration & Update

And this one: https://www.bikeforums.net/classic-v...storation.html

This one looks like the same color as yours: https://johns-recycled-bicycle.blogsp...storation.html