It is very interesting...especially because it's not stapled to the cover. The Gold cover is almost like a printer's proof that someone kept.
I don't think anyone really knows for sure which just adds to their mystique. However, I tend to believe there were 150 copies created of each. I say this for two reasons.
First, this is the number that's documented in the publications (like Turtlemania and some magazine/newspaper articles) from the early days of the TMNT. I think this would be the most accurate record since E&L surely had more accurate recall of the their efforts to produce them after only 3 years had passed. As time passes, memory fades and second-guessing comes into play.
Second, 50 copies of each doesn't seem like it would be a sufficient amount to properly promote or advertise their work and the upcoming TMNT #1. I would think they'd burn through 50 copies of these quickly. Plus, this was a hand-made comic book...they had to know that many people would simply discard them or toss them aside as rubbish. Knowing that, I think they would have printed more than they thought they'd need.