This dealer claims to sell RTL5370, In my case a RTL8188EU arrived.
http://www.amazon.co.uk/gp/product/B00EZOQFHO?ref_=cm_rdp_productThis is what dmesg reports when loading it:
[ 1607.074976] usb 1-1.2: Product: 802.11n NIC
[ 1607.074993] usb 1-1.2: Manufacturer: Realtek
[ 1607.075009] usb 1-1.2: SerialNumber: 001D43303B0F
[ 1607.124790] r8188eu: module is from the staging directory, the quality is unknown, you have been warned.
[ 1607.133405] Chip Version Info: CHIP_8188E_Normal_Chip_TSMC_A_CUT_1T1R_RomVer( 0)
[ 1607.183886] usbcore: registered new interface driver r8188eu
[ 1608.014322] MAC Address = 00:1d:43:30:3b:0f
[ 1608.018644] IPv6: ADDRCONF(NETDEV_UP): wlan0: link is not ready
Chip version info looks a bit iffy. I could not get it to act as an access point though some on the net claim success after much fiddling.
I thought it may get proper support from the new PI O/S Jessie (just out) but that spouts the same warning.
I bought another off EBAY that was a 5370 and is working. Packaging identical!!
I think it's a lottery.