Transistor ID needed

Hi, I am trying to ID a transistor in a TO-220 package with part # P55MF06L printed on it and the manufacturers logo is "ST" and is printed on the lower left corner. A Google search turns up nothing on this part.

I think that number is unlikely for an ST device. More likely is P55NF06L, being an N Channel Mosfet

Yes, you are correct on the part number. I took a closer look at it and it's a letter N; not M.

Manufacturer code ST is for the french company SGS Thomson.
They are a large and reputable manufacturer of semiconductors.
ST and STM are typical markings used.
Their website is www.st.com
Its a very informative and very professional web site with all the information you would need.