Hi, I was wondering how to identify which model french horn I have. Where is the serial number located and is the model number marked someplace or is it just associated with the serial number? Thanks!! The horn is a silver plated double horn marked C.G. Conn

serial numbers can be different places.
model numbers are sometimes stamped on the end of the leadpipe.

One way to tell is to follow the lead pipe if it goes about 16 inches before it comes to your first main tuning slide which is on the underside of the horn you probably have an 8D.

If the leadpipe crosses up to the front or top of the horn for your first tuning slide you have a 6d (except 6d's are yellow brass, so it would be a different model).

That would be step one.
Step two would be to locate where the thumb trigger valve is.
Is the valve the thumb trigger operates near the mouthpiece or on the other side of the three valve rotors?

If it is near you, and the tuning slide is on the underside, and it is nickel silver you probabyl have an 8D horn. Look for the serial number on the second valve rotor casing, or under the 2nd valve lever under the spring.

<Added>

Correction - there are silver Conn 6D's.

I found the model number, it says 6D. Do you have any idea how much it is worth? I'm probably going to sell it as I inherited it from my brother. I am a saxophonist....

Brand new Conn 6d's sell for about $2400.
A used one in great condition I have seen people asking $1200-1500.
A Conn 6D in good condition will sell for $500-$700.

I am curious as to your horn specifics. Can you send pictures to my PM. I question whether it is truly a 6D as I sais earlier I think 6D's were only made in brass. I don't know of any in silver or nickel. If you send me pictures I can more accurately identify it.

I have read this short strand and am a band director but am still having trouble figuring out the model of a used nickel silver Conn double I bought. The main tuning slide in on the bottom about 16 inches from the mouthpiece. The trigger in up near the mouthpiece and the serial number is on the valve bar below the key spring. How might I know if this is a 8D or possibly a 10D?

A Conn 8D is a Kruspe wrap - the thumb valve comes before the other valves.
A Conn 10D is a Geyer wrap - the thumb lever operates a long linkage that moves the valve which is past or after the other valves.

Thanks. It has to be an 8D. According to information I found about serial numbers it looks like it was made in March of 1978 and is in pristine condition. Any idea on how much it's worth?
Thanks.

Ah, you have an Ablilene horn.
This was a big change period for Conn. New technicians and new craftsmen new tools and lots of inexperience.
As is it is a good repectable horn, but not to par with the older pre-letter series, or K series.
What is it worth? whatever you can get for it, but I wouldn't expect more the $2K.
If you decide to continue to play and want to upgrade the horn, contact Patterson Horn works. He has a 'rebuild kit' so to speak. What he does is goes in and cleans up the questionable solder joints that might have solder hanging inside disrupting the air stream; or uneven solder joints. He also includes a leadpipe change and an extension tube change over. This will improve the horn response, evenness of tone and certainly upgrade the value and worth of the horn.
But if you bought it to play and it works and you like it then it's worth just that!

I own a 6D which, according to the serialnumber ( 305XXX ), must be build about
1935 / 1936. The horn is silver plated and some of this plating is gone due to it's
age and use. Furthermore it has a few little dents but nothing serious !
The sound and playability of this respectable oldtimer are amazingly good; it has an
easy response and good intonation. The tone is warm and full ( I'm using a
Farkas MDC mouthpiece ).
Is there any clue what the worth of such an instrument is ? Here in Europe I found
not so many expertise about US made french horns. Holton is the best known I believe.