What could it be? Hmm... Try complete the picture!
4 1 25 (In this exact order)
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I think the complete picture looks as follows
If we convert the numbers in the large triangle to letters and read from bottom right clockwise, it spells out DAY. Given that the circle has seven concentric annuli, we realise that it has to do with the days of the week.
Now, we know that in English before the DAY part of the word, each day has either 3,4,5 or 6 letters and the circle is split into four quarters denoted by a triangle, square, pentagon and hexagon. If we assign the inner annulus to Monday and proceed outwards, the process is to shade in the quarter of the annulus which corresponds to the number of letters in the first part of the name of the day of the week - so Monday, Friday, Sunday in the triangular quarter, Tuesday in the square quarter, Thursday and Saturday in the pentagon quarter and Wednesday in the hexagon quarter.
Well, it could be
a terminator vision aiming grid
so you would complete the picture like this:
original image copyright these guys (GPL3+)
(..Yyyyeah, sorry, I may have had a few..) X-]