I have several different models of vintage Tasco porros, but the model 100 is not one of them. However, they are all far more alike than they are different. The best way to tell which is which is to look at the label on the prism plate, they are that close. Internally they are all carbon copies and I think the internal parts may well interchange, but I confess to not having tried that
. My favorite is probably the Tasco 116, which is about the only one different internally from the others, in that it has smaller prisms and it all fits into a more compact body and is thus smaller than the others, but aside from the size scale, there seems no difference.
They are all easy to take apart, but you have to be careful because at some point Godzilla must have worked at Tasco (or Nitto Koki Co. which made most Tascos). Some stuff can be ungodly tight.
With taking as little apart as needed, run the focus to the point where the oculars run as close to the prism plate as they will go, remove the cover on the objective side of the hinge. That may uncover a couple of the too tight set screws, but leave them be and look up the hole and you will see a screw head which holds the focus rod and the ocular mechanism. Loosen the screw until it comes out of its place. It won't come out of the binocular if you leave the rest of the hinge cover in place.
At this point reverse the focus direction and gently run the focus knob until the focus rod and attached oculars come loose. Set this aside on a clean paper towel and cover with another. The ocular tube can then be removed, but beware, Godzilla may have installed that too. You may need a small strap wrench, padded pliers, and/or maybe a carefully whittled (to fit inside the ocular tube) dowel to loosen it. This is a potentially ruinous operation so be careful, especially screwing it back together. Take it out and then remove the screws from the prism plate and the plate can be removed, exposing the internal prism mounting. That plate is held in place by three screws, which can be removed and the prism mount can then be lifted out to expose the internal glass surfaces. If the binocular is collimated I try my best to not remove the objective lenses assembly unless I want to recollimate. If that has to come out to clean fungus, be sure to note the respective orientation of the eccentric rings and the position of the adjustment slots. But you can get access to all of the inside glass surfaces from here. That fungus should be removed or it will eventually etch the glass surface it grows on.
Reverse procedure to put back together. If I can do this you can too. Just be careful and patient.
EDIT to note that on the plate that mounts the prisms, there are also three very small set screws there that can serve to manipulate the prism angle. DON"T mess with those other than to be sure they are just barely in contact.