This brand was designed by a Polish immigrant who escaped his country during the second World War. It is a long running brand with a colorful history, but the "Nelco" sewing machines do not seem to have much interest within the collectors of antiques. In order to figure out the type of "Nelco" sewing machine that a person owns, or to get a manual for it, it is important to know its model number.
Place the "Nelco" on a solid surface off of the ground such as a table or a desk so that you can good access to it and do not have to get in an uncomfortable position to examine it. Use your legs and not your back when lifting in order to avoid injury as these are heavy machines.
Look alongside the bottom of the machine on all sides, as many will have a metal plate with the model number on it located on the side, front or back.
Tip the machine on its side and take a look at the bottom as this is another location where the model number could be placed.