Martin Luther was a theologian who lived in the 1500's. In a letter to his friend Lazarus Spengler (1530 AD), Luther wrote: "Grace and peace in Christ: Honorable, favorable, dear Sir and Friend! Because you deeply desire to know whether my [personal] seal has [hit the mark/appears correctly], in good humour/amiability, I present to you my first thoughts which I want held fast to my seal as a symbol of my theological teachings:"

(Pictured here is a flyer printed circa 1617 in celebration of the Centennial Anniversary of the Reformation.)

Examples of Luther's Seal

Lutherrose on the Schlosskirche Wittenberg
 photo courtesy Rainer Oettel
Martin Luther's 1530 version of his rose emblem, with color
(Detail of Centennial flyer)
By artist Hans Philipp Walch, printed in celebration of the Centennial Anniversary (1617) of the Reformation.
LUTHER DESCRIBES THE SYMBOLISM

"The first (thing) should be a cross: black in the heart, so that I myself would be reminded that faith in the Crucified One makes us happy. For when someone believes from the heart, so will that person be justified. [Romans 10:10]. Although it is a black cross, which mortifies and which should also cause pain, yet it doesn't make the red heart black. It does not spoil nature, that is to say, it does not kill but keeps (the heart) alive. For the just shall live by faith, yet by faith in the Crucified One [Jesus]. [Romans 1:17]. 

But such a heart should stand in the middle of a white rose to show that this faith gives joy, consolation, and peace. And [this heart is] directly set within this white, cheerful rose - not how the world gives peace and joy [John 14:27] (that's why the rose should be white, and not red, because the white color is the spirits and all the angels' color). [cf. Matthew 28:3; John 20:12]. 

Such a rose stands in a sky-blue-colored field, (to show) that such joy in spirit and faith is the beginning of the future of heavenly joy - yet now inside, understood, and through Hope is grasped, but not yet apparent [revealed]. 

And [around] this field is a golden ring, [showing]that such bliss in heaven eternal will endure, and it has no end, and is also comforting above all the happy things and wealth, like how gold is the highest, most precious ore. Christ our beloved Lord be with your spirit until [we are in] that life, Amen."