It will be above the right side fender on the horizontal brace for the upper feed roller real close to the vertical disk housing. It should also be on the vertical metal piece below the round sticker you can see in the picture.
That's like a 1984 Eeger Beaver model 100 though I'm not sure they even used a model number back then. Should be a 4 cyl Ford gas engine or Wisconsin 65hp.
Number should be on the tongue but who knows. I have come across old units that never had a number stamped into it.
When I called morbark about mine, I was told it was on the side of the disc housing and on top of the upper feed wheel arm mounting bracket. Nothing was said about it being stamped into the tounge