Finally we get those information, I also guessed its hashrate should be about 50 mh/s. Btw, have you tested it with other algo, for example mining Monero? One month ago 775$ per card is a good deal, but now it's hard to say as Bitmain's going to release asics miner E3. Even me, I'm going to switch all of my Rx580 rigs to mine Monero in next month. Claymore already added new string for Monero hard fork. Hopefully Ethereum will have some move on it.
Keep in mind that these GPU's only have 3200 CUDA cores versus a 1080 Ti which has 3584 CUDA cores. The P102-100 has optimised memory timings and is hence faster for memory bound algorithms (such as Ethash used for Ethereum mining), but slower for compute bound algorithms (such as CryptoNote for Monero and Equihash for Zcash mining).
Zcash benchmarking with DSTM shows around 675 sols/second at stock clock speeds. I achieved a maximum of 710 sols/second with a +100 mhz core overclock.