I don't know where else to post this. 

I'm posting this for someone else, an older retired person without email or web access. He can't ride this bike any more, knee problems, and moving to Arizona.  He asked me to help him sell it. 

Men's bicycle, 21-inch frame (crank-to-seatpost).  It had the name "Rialto-Signal" on it, and says a "cross series".

28 x 1-5/8" tires on the wheels, and includes a spare rear wheel with gears.  It looks like a 15-speed bike, 3 front, 5 rear.  Includes a chain lock and two saddles - the original saddle which was replaced because it wasn't comfortable. It has fenders, and a rear rack. It's in good shape, and has been kept inside.  The tires are practically new. It is a heavier bike.  

Is anyone familiar with this bike?  Would anyone care to estimate a price to sell it for?  How do you sell something if you don't know what it's worth?