I think the dust on the horn makes it look like an 8.  So I am adding another pic to really determine and then I can go from there.  Thanks for all your help.

I agree with Mark above.  It really cannot be a 3 since the 10M model you show was not made when Conn was making the 230XXX serial number horns.  The number 280XXX would put the horn in 1937 - 1938 which are very desirable years for the 10M.

I suspected that the serial number you posed originally was off, and that was why I aked for a photo of that area.  It is not at all unusual for a horn of that age to have some buffing/wear in the serial number area, especially if the horn has been relacquered since many buff the horn with an abrasive to remove old lacquer or surface contaminants before replating.  I have seen many horns that display this issue. 

Thank you for the response. Any idea of value as is?

Well I have already stated that I am not the best person to assign value, but I'll give it a rough shot that you can use until someone who really knows their stuff chimes in.

First off, the value depends a lot on not just the model and year of the horn, but also on what the condition is and whether the lacquer is original or a relacquer.  Even a rather well worn horn with original lacquer is worth a lot more on the market than a relaq.  (This is crazy to me, but I don't make the rules).  From the photo of your horn, I think it is a relaq.

The next important issue is the playing condition of the horn, and how much extra expense a buyer faces to get the horn to play well.  If this horn has been recently serviced, has good pads (such that any additional service faced by a buyer would be minimal), I would estimate the value of the horn somewhere between $2K and $3K.

From your correspondence, I assume that you are not a player, and the horn has been sitting around for awhile and may need significant service to play well.  A full overhaul of a horn can easily run around $1K, so that would place the horn value in the $1K to $2K range.

I know that this is a broad range, but to get any closer, one would need to inspect the horn, or at the least see a whole lot more photos.  I hope that someone who is really in tune with the market jumps in and gives a better estimate for you. 

Thanks again you have been a great help.