Iron Fireman furnace

I inspected a 1955 home in Denver with a Iron Fireman natural gas furnace with model #FGLB-135N and serial #GFB-1299. Was this originally an oil burner converted to gas with a pilot light (65% effficient?)? I could not find much information for this unit? The unit was operational with blower motor in working condition. Had two filters, a washable and a 16X20X1 disposable. I have included a picture of the ID tag and the burn chamber (heat exchanger). Please provide me with any information you can on the furnace. By the way, due to the age, do you recommend further evaluation by HVAC technician?





Although it was a good manufacture , it is old. if your not sure on operation state so and recommend a qualified heating company .There may be nothing wrong with it, but the your client could save a fair amount by changing it( depends how cold it gets there)