Option Codes

Can someone tell me the difference between these 2 MRK Jan 2006 calls at 27.5.

Calls LastSale NetChg Bid Ask Vol OpenInterest

JAN 2006 27.5
MRKAY 2.60 1.40 2.30 2.60 262 7,674

JAN 2006 27.5
WMRAY 6.60 0.20 6.60 6.80 29 7,780



I got AY means Jan 27.50, MRKAY makes sense just not sure what the WMR one is...

Thanks.

 

All Jan '08 MRK leap calls start with WMRA. However, there is no such option as WMRAY.

 

I can only find quotes for WMRxx Jan 06 options in archived pages from 2004. Maybe they renamed the '06 WMRxx options to MRKxx when the '08 options became available?