First of all,... in my humble opinion the reflection does not need to be tack sharp. As a shallow depth of field can be very appealing, also here a blurry reflection can be attractive.
But this was not the question. The question was how to get the reflection sharp. I’m not a physicist, but I have some ideas why JackieR’s reflection seems blurry.
1. As the glass is 3mm thick, the light (aka image) is reflected from the top layer and the bottom layer of the acrylic glass. This gives two mirrored pictures that are refracted by the 3mm difference and those two pics appear blurry for our eyes.
2. Probably there is an optical coating on the perspex sheet. To avoid reflections.
3. Angle. If you look at your setup from the side, you will see, that your lense stand in an angle to your objects. Makes a difference to the original object, and the reflected object. Depending on the aperture, the focus is not in the dof.
I know my English is kind of weird and often I can’t express myself clearly, so I made 3 quick shots, to show the results of 3 different layers. (BTW, the battery of the watch is dead).
All of the shots are lovely but I can see (although it's small) that the center one seems to be the clearest. Now to get something that's laquered and black.
If took me ages to set mine up, bet you did these in a flash!!
Thank you again 😸