How would one find out?
Does your jeep have a passenger seat?
Does it have a harrison heater?
Does it have either PTO?
Those are the easy ones. The others take a little investigating.
If the footman loops on your tailgate have sheet metal acorn nuts, then it had a factory soft top.
I vaguely remember reading something about dual tail lights. I'm not sure what the details were about it, but when I checked my '53, it did. I think you could get either no reflector, reflector, or a tail light on the passenger side. I could be 100% wrong on this. Bob W will know. However, my '49 had no holes for nothing on that side.
As others have mentioned, you would have some roller clips at the very back of you bed for the rear seat to snap into. My '49 doesn't have them.
Of course, you will only know if your jeep hasn't been restored with some of these items. Most people add two tail lights, put a new tailgate on and add PTOs. So you may never know what it came with.