[mikethedruid]

Without more pictures of the Transformer, closer, showing the mounting more clearly, it's hard to say if it is original., but, looking at the topside picture, with the holes to the right of the transformer, it makes me wonder. The "tar" you see is a sign that the transformer was running somewhat overloaded for some time, got hot, and the insulating tat inside it melted. This can be a result of operating with a bad filter condenser in the power supply, or other heavy load on the B+ supply. I've seen a bad filter condenser cause the plates of the rectifier tube to actually glow red. If allowed to continue for a few minutes like this, the load can overheat the transformer to the point the tar melts.