Hi Patrick

 In case you have multiple crystals in the solution, you can pick up a few crystal and re-suspend in water or a suitable buffer and run it on SDS-PAGE followed by Silver Staining procedure.

 Or, if you have access to the Mass Spectrometery, you can give the solution for simple MALDI-TOF and a peak at proteins mass will show up in the spectra. NOTE: To improve the results, try washing your crystal in the mother liqour (Buffer in which protein was there + ur condition in exact ration as used while crystallization setup). You can transfer the crystal in this drop and then pick up again to re-suspend in water. This will remove errors from protein picked up in the solution as residual volume of loop.

Patrick, someone in UPenn will have UV microscope and UV transparent plates. Transfer your crystal into one of those plates and see if they glow.

You can use a needle to feel if it is hard to crash the crystal; protein crystals are soft and easily breaks apart

Hi Patrick, if you can spare two three crystal then you can try Hamptons Izit dye, please fins details: https://www.hamptonresearch.com/documents/product/hr006810_4-710_izit_user_guide.pdf , 

All above four suggestions (SDS, izit dye, crush using needle, mass spec) are good one and workable. Good luck. If you have a x-ray diffractometer, you can expose to x-rays and that will give you an exact idea. If you have Raman spectroscopy, you can try as well.