If the grates are the same size, then the stove is a Hyfire II. The 40 grate is much smaller then the 90 grate.
The main reason for the 2 ports is to get heat into the basement if your hooked into a hot air jacket. With a jacket 85 % of the heat is being put into your duct work. some people want a little extra heat in the basement. So we built 2- 2x4 tubes as small heat exchangers through the stove. You can open 1 or 2 or none, but we have them there for that little extra. I talk with people everyday, everyone wants the applacation a little different. We do as much as we can without adding too much cost to the stove. People burn coal to save money, if the payback of the stove takes 20 years, well then it just not worth all the extra work. Have a good day.