Unfamiliar tubes for a preamp

I will be in reciept of a BEZ preamp that uses what the previous owners says are one 15z4p and one wy4p tube in addtion to two ecc88 tubes that my current pre uses. Could someone tell me what these tubes are or other numbers I can look up. They sound like rectifiers. Thanks in advance and enjoy the music.
The EC88 is a European designation for the 6DJ8/6922/E188CC/7308 family, and is a dual triode. The Holy Grail of the family being the Siemens CCa. The WY4P is a chinese voltage regulator tube like the RCA OD3 (http://cgi.ebay.com/NOS-0d3-VR150-JAN-RCA-MADE-IN-USA-TUBES-OD3_W0QQitemZ330230807107QQcmdZViewItem) Change yours for an RCA, and you should realize quite a sonic improvement. There is a 5Z4/5Z4P full wave rectifier tube, but I've never heard of a 15Z4P.
Thanks Rodman99999 for the info. I knew about the Ecc88 but was in a fog about the others. The 1 in front of the 5Z4P tube was probably given by mistake. I'll check on the RCA OD3 once the pre arrives. Thanks for the link.
One other question comes to mind on the rectifier tube. It looks like a GZ30 tube is the same as the 5Z4. Could someone verify this. Thanks in advance.