EFM steam boiler vs. hot water???

Can anyone tell me the difference in design between an EFM steam boiler and a EFM hot water stoker? Can a coal-fired EFM steam boiler be used or
retrofited to a hot water baseboard appilcation? Was the 520 made in both steam and hot water configurations? If so, are most components the same?

The 520 boiler can be used for steam or hot water. The only difference in the kits are the controls. If it has been used for steam and not properly set up or maintained, look for rust damage. Otherwise, it's the exact same boiler and stoker.