Ambiguous line from Browning's My Last Duchess [closed]

A heart – how shall I say? – too soon made glad,

Too easily impressed: she liked whate’er

She looked on, and her looks went everywhere.

Sir, ‘twas all one! My favor at her breast,

The dropping of the daylight in the West,

The bough of cherries some officious fool

Broke in the orchard for her, the white mule

She rode with round the terrace – all and each

Would draw from her alike the approving speech.

What does the phrase My favor at her breast mean in the context of this poem? I am not sure about how it should be interpreted.

For favour(n.) OED gives

7.a. (concrete of 1.) Something given as a mark of favour; esp. a gift such as a knot of ribbons, a glove, etc., given to a lover, or in mediæval chivalry by a lady to her knight, to be worn conspicuously as a token of affection. 1592 Greenes Groats-worth of Witte sig. C3v She..returnd him a silke Riband for a fauour tyde with a true loues knot.

1598 W. Shakespeare Love's Labour's Lost v. ii. 130 + 1 Holde Rosaline, this Fauour thou shalt weare.
:1712 Spectator No. 436. ⁋6 That custom of wearing a mistress's favour on such occasions [fencing contests] of old.

And even manages to quote your example as their example:

1842 R. Browning My Last Duchess My favour at her breast.

Whereas originally, favo(u)rs were rarely of any great monetary value - their purpose was simply to be visible on one occasion - usually a on a knight in a fight, This is a favor that the Duke has given to his wife. I suspect that this therefore is not a "real chivalric favor" but more a "love token.

As far as I am aware, men did not give out favours (in the "knightly" sense) to women.

If you look at https://www.medievalists.net/2016/02/five-medieval-love-tokens/, you will see that the favourite candidate is a brooch - displaying love and the wealth of the giver.