Nice horn!  That looks like a very early "Revision A" (going by the bell strut) tenor made by Strasser-Marigaux-Lemaire.  You can check pictures and serial numbers under this link to be sure.

http://saxpics.com/?v=man&manID=19


The body looks straight and it looks like intact original lacquer.  A rare find to be sure.
You can get an idea of what a dealer might charge for it under this link.

http://www.saxgourmet.com/VINTAGE_SAXOPHONE_VALUE_GUIDE.htm

You should probably expect less as a seller.  You should also deduct the cost of any needed repairs (in this case probably pad work and adjustments) from its value.  Get an estimate for that work from someone who knows vintage saxophones.

The price depends with the condition, Years, complete accesoiries and The Brand