A lady does not begin a recommendation: "To whom it may concern," nor "This is to certify," although housekeepers and head servants writing recommendations use both of these forms, and "third person" letters, are frequently written by secretaries.
A lady in giving a good reference should write:
Two Hundred Park Square.
Selma Johnson has lived with me for two years as cook.
I have found her honest, sober, industrious, neat in her person as well as her work, of amiable disposition and a very good cook.
She is leaving to my great regret because I am closing my house for the winter.
Selma is an excellent servant in every way and I shall be glad to answer personally any inquiries about her.
(Mrs. Titherington Smith)
October, 1921.
The form of all recommendations is the same:
...................... has lived with me ........ months/years as .......................
I have found him/her ....................... He/She is leaving because .......................