Looks like the 3160 that I have on my 184 LoBoy.
Mine has a steel cover plate on the left side (EBay item) and is open on the right. Search for IH 3160 and you can find the parts blowup. I presume that it is a safety feature, if you mt/dismt from the left.
There is also a steel rock guard that bolts to the front edge. Looks like yours is rubber(?)
The back is open on mine, and that's a good thing as this model discharges poorly out the side if 1) the grass is a little damp, 2) the grass is too high 3) all of the above.
If #3 occurs, the clog will stall the mower blades! Another PITA! Apparently improvements were made on the 3160A model and the Woods. Would probably cut better with the left safety guard off!