Does anyone know of any (or every) book by a Reformer or Puritan with an epistle dedicatory addressed to a civil magistrate.

So far I have found ones in Lewis Bayly's The Practice of Piety, and Edward Fisher's The Marrow of Modern Divinity.

Calvin has one in the Institutes, but I am not sure if there is anything about the magistrate's duties in it. I will have to check it out if no-one can remember.

Zwingli has one to the king in his work On True and False Religion. I'm scanning it in tonight. Will send it to you when I'm done. He also has a chapter on the Magistrate.

Check out Bullinger's Decades. The third and fourth Decades contain dedications to King Edward VI. The fifth Decade has a dedication to the Marquis of Dorset. You may wish to review the others to see about additional dedications.

Calvin's commentaries contain numerous epistles dedicated to magistrates.

Bucer's De Regno Christi was dedicated to Edward VI.

The Belgic Confession was primarily addressed to Philip II.

Myles Coverdale published a Bible with an epistle dedicated to King Henry VIII and Erasmus' Paraphrase dedicated to King Edward VI. The 1560 Geneva Bible was dedicated by William Whittingham to Queen Elizabeth.

Originally Posted by VirginiaHuguenot

Check out Bullinger's Decades. The third and fourth Decades contain dedications to King Edward VI. The fifth Decade has a dedication to the Marquis of Dorset. You may wish to review the others to see about additional dedications.

I got the RHB edition at John Gowan's a couple of weeks ago; looks good.

Witsius' Economy of the Covenants has an address to King William III.

Originally Posted by AV1611

Witsius' Economy of the Covenants has an address to King William III.

Is this in modern reprints? Does it contain anything on the duties of the magistrate?

Originally Posted by Daniel Ritchie

Originally Posted by AV1611

Witsius' Economy of the Covenants has an address to King William III.

Is this in modern reprints? Does it contain anything on the duties of the magistrate?

Yes, at least it is in the 1990 reprint of the Den Dulk Christian Foundation.

There is a little bit on the duties of the magistrate, but the bulk is praise for the King. A better bet is Martin Bucer's De Regno Christi -- it's entirely about the duties of a Christian magistrate.

Francis Turretin's dedication in the Institutes of Elenctic Theology addresses civil magistrates and their duties.

Most magnificent, noble and honored men of the consul and all the Senate of the celebrated Republic of Geneva, health and happiness is desired for you from Francis Turretin.
...
These the authority of your predecessors firmly restrained and happily put to flight, so that always with great praise, they approved themselves to be "strenuous and hearty defenders of the cause of piety," the honorable utterance which that most distinguished man of God, Calvin, formerly used concerning them.

That this is also your principal care, most watchful fathers of your country, your zeal and piety do not suffer us to doubt. For indeed you have remembered that dominion is strengthened by piety and righteousness according to the oracle of the wisest of kings; and that your rule never could be happy and well ordered unless you took care that by the word of God, his authority should always avail with you and that Christ himself should reign through you. You have remembered that here might be not so much an aristocracy as a theocracy, having God always for its president and ruler; and that the safety of the republic, which should always be the supreme law, could not be better consulted than by defending those two impregnable ramparts -- the culture of pure religion and the pious care of nurturing the church, which God has committed to the protection of your wings. This has been so accomplished thus far by you that not only has religion remained here uncontaminated by any corruption of error and superstition through the special favor of God, but nothing besides has been changed in the purer doctrine once received here, which you have bound yourselves always religiously to be retained. Go on, Lords, constantly in this sacred purpose and cause, by your pious and unwearied vigilance, these good things to be perpetual to us; so that under your auspices this republic may always be happy and flourishing in piety even to the latest posterity. This undoubtedly you can hope from God, who has promised to be a guard of those cities which would be the seats of truth and the refuge of the pious as long as you will always be solicitous about religiously worshipping and retaining him and promoting his glory above all things; as long as you will take care that among your citizens piety and justice, the love of religion and of country, love and the holy concord of souls shall flourish, and vices (too many in this most corrupt age even in the growing church) be severely repressed; as long as by our zeal this city shall truly correspond to her name "Reformed," as much with respect to integrity of morals as to purity of doctrine (and, that I may speak the word, the "city of God" and true chptsybhh, in which shall be the good pleasure of God).

Thomas Cobbet has a dedication to Oliver Cromwell in The Civil Magistrate's Power.

Originally Posted by VirginiaHuguenot

Thomas Cobbet has a dedication to Oliver Cromwell in The Civil Magistrate's Power.

Thanks, I have got that one.

The first volume of William Greenhill's Exposition of Ezekiel was dedicated to Princess Elizabeth, daughter of King Charles I and queen of Bohemia.

The Bible-battells. Or The sacred art military For the rightly wageing of warre according to Holy Writ. Compiled for the vse of all such valiant worthies, and vertuously valerous souldiers, as vpon all iust occasions be ready to affront the enemies of God, our king, and country (1629) by Richard Bernard was dedicated to King Charles I.