Aaron,
There's an easy way to verify it.
Just use a fine grid - Rochi screen 100 lines per mm - a piece of fine mesh will also work.
Point the scope at a bright star, remove the eyepiece and place the grid over the end of the focuser. You should see a series of fine lines. As you re-focus, and get closer to the focal point of the mirror, the number of lines will reduce, and their width increase.
When you have 4-5 lines, look at their straightness - if straight, the mirror is parabolic, if curved then it's spherical.
HTH
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