Heating Help

National Convectors

I bought an old farm house and has hot water convectors on the walls. These are marked National Art Convector, National Radiator Co.  I know very little about them, they have "fins" that would remind me of a baseboard but a large metal cabinet. Can anyone tell me what the age of these is and any other info about them.  I am thinking about going  to old cast iron radiators in the house but would like to know more about these convectors.  I have included a few pictures that may help.

those

are 50's-early 60's. Although cast iron is the best, JMHO, these were damn close. 

"Every Darn Radiator"

There's a book Dan's got out - EDR - Every Darn Radiator. The're in there. How old is the house?
                                                 John Pughe

Recessed Convectors:

The one on the right is a recessed convector.
They work fine.