The meaning of モン in 上手いモンでしょう

Question

The main characters younger sister showed him some scribbles she had done in her textbook and then said 「上手いモンでしょう」.

My question is whether it is definition 5 here or whether モン refers to the scribble itself.

Answer 1

It is definition 5-㋑.

「[上手]{うま}いモンでしょう」 is, in my own words, an "exclamatory rhetorical question".

= "Looks awesome, doesn't it?"

The "statement" form using this 「もん」 would be 「上手いもんだ/もんです」.

So, 「モン」 does not refer to the scribble itself.