- Good job
-- On the subject of perspective these classes are only scratching the surface. We are not treating oblique lines. In most cases their correct form can be derived from the context, for instance the roof of a house:
For very small parts as on this clock, you wouldn't see the difference between a "calculated" direction and one that is drawn intuitively.
-- Finding the centre of a rectangle and drawing concentric rectangles - in any perspective -is by the two diagonals:
If you intend to draw realistically, try to observe the proportions. This time your clock looks rather cartoonish. For instance the plinth of the top part looks out of proportion.
Keep up the good work