This report on the Mozarts in Paris is similar to a known report published in the Wienerisches Diarium on 23 Jun 1764 (no. 50, [4]; transcribed in Dokumente, 37); however, the Berlin report precedes the Viennese one by more than two weeks, and may have been its source. The version in the Wienerisches Diarium reads:

(For errors in the transcription of this report in Dokumente, see the Notes below.) 

There are several significant variations in wording between the two reports, and it is possible that the report in the Wienerisches Diarium was not copied from the one in the Berlinische Nachrichten; it may be that they derive from a common (but currently unknown) source. The report in the Berlinische Nachrichten includes one sentence not present in the Wienerisches Diarium (“Da diese Kinder ihres gleichen in der Welt noch nicht gehabt haben, und vielleicht nicht mehr haben werden, so ist es kein Wunder, daß sie dem Hofe zu Versailles ein ganz ausserordentliches und unbeschreibliches Vergnügen gemacht haben”), while the report in the Wienerisches Diarium closes with a sentence not present in the Berlin version (“Wie entwickelt sich nicht öfters zum Erstaunen, in dem zartesten Alter der Geschmack, der eingebohrne Trieb zu ein und der andern Gattung schöner Künsten”). The Berlin report gives an incorrect date for the Mozarts’ departure from Paris (they departed on 10 Apr 1764, not 29 Apr); the date is not present in the Vienna version.

Both reports refer to a present given to the Mozart children by the French court, as well as Wolfgang’s dedication of keyboard sonatas to Madame Victoire de France and her present to him of a tabatière (snuff box) worth 80 Louis d’or. (The Diarium corrects the transposed characters in the name “Victorie” in the Nachrichten.) These two reports are the only known sources for the claim that Madame Victoire de France gave Wolfgang a present of this sort and value as a reward for op. 1.

In Feb 1764, the Mozarts had received a gift from the French court of 1200 livres (50 Louis d’or), as noted in the records of the king’s petty expenditures (“Dépenses des Menus”; see Dokumente, 30). This is undoubtedly the gift to both children that is mentioned in the Berlinische Nachrichten and the Wienerisches Diarium (in fact, these two reports seem to be the only known public references to the gift). There is no reference in Leopold Mozart’s correspondence or any other known document to a gift of a gold snuff-box from Madame Victoire de France. However, Leopold does mention in a letter to Maria Theresia Hagenauer on 1–2 Feb 1764 that Wolfgang had received a gold snuff-box from the Countess de Tessé, who was to be the dedicatee of Mozart’s op. 2:

Außer dem was wir vom Hofe zu hofen haben, haben wir in Versailles mehr nicht
als 12 Luois d’or [sic] in Geld eingenommen. Dann hat mein meister Wolfgang von
der Madme la Contesse de Tessé eine Goldene Tabattier, eine Goldene Uhr, die, wegen
hrer kleine kostbar ist, und davon die Grösse hier anzeige. [Briefe, i:124]

Apart from what we can hope to receive from the court, we have taken in no more
than 12 Louis d’or in cash in Versailles. Then my master Wolfgang received from
Madame the Countess de Tessé a gold snuff-box, [and] a gold watch, which, on account
of its small size is precious, and of which I draw the size here [Leopold draws a circle
representing the size of the watch].

It is possible, then, that the reports in the Berlinische Nachrichten and the Wienerisches Diarium were mistaken about the identity of the donor of the snuff-box: perhaps the gift referred to in the reports was the snuff-box given to Wolfgang by the Countess de Tessé. On the other hand, it cannot be ruled out that Wolfgang received two gold snuff-boxes, one from the Countess de Tessé, and one from Madame Victoire de France, as a reward for op. 1.

The Louis d’or was a gold coin, first introduced by Louis XIII in 1640, with a profile of the king on one side and a royal coat of arms on the other. Louis d’or were subsequently minted with the profiles and arms of the next three kings: Louis XIV, Louis XV, and Louis XVI. In 1726 the value of the Louis d’or was fixed at 20 livres, revalued in 1740 to 24 livres, where it remained at the time of the Mozarts’ visit. Thus the 1200 livres recorded in the king’s petty expenditures as a gift to the Mozarts was equivalent to 50 Louis d’or, which may, indeed, have been the type of coin they actually received.

The topic of exchange rates between French currencies and German ones during the time of the Mozarts’ tour is an extremely complex one, owing mainly to the diversity of German currencies; it seems likely that the last word on these rates remains to be said in the Mozart literature. Leopold himself confused matters for later scholars by giving different rates in different letters to Lorenz Hagenauer. In a letter to Hagenauer from Frankfurt on 20 Aug 1763, Leopold writes of a “Geld=Devalvations=Tabell” (“Money-Devaluation-Table”) in Frankfurt that sets the value of a Louis d’or at 11 fl (11 gulden; see Briefe, i:87). This is the exchange rate for the Louis d’or used by Ruth Halliwell in her study of the Mozart family (Halliwell 1998, 61, note 1, and passim). In a letter to Hagenauer written from Paris on 8 Dec 1763, on the other hand, Leopold describes a rule of thumb he has developed for judging French monetary equivalences:

Der Louis d’or hat 24 Livres; folglich 4. Cronthaler sind ein Louis d’or, dann ieder
Laubthaler gilt 6. Livres. Ein Livre hat 20. Sols. Ein Sols hat 4. Liards. Wenn sie nun
die Liards für Pfenning gelten lassen; so gilt ein Sols einen Kreuzer, folglich der
Livre 20. kr: ein Kron=thaler 2.f: der Louis d’or aber 8 f: nun gibt es keine Münze
mehr, als die Six Liards Stücke, die nach meiner Meinung 6. Pfennige sind, und
die 2. Sols Stücke oder 2. Kreuzer, die douze Sols Stücke oder 12 kr: Die Vingtquatre
sols oder 24 St: Nun wissen sie alle Geld Sorten denn keine andere giebt es nicht in
Franckreich. Ich weis wohl, daß der Louis d’or mehr als 8 f: werth ist etc. allein mit
dieser Rechnung komme ich besser zu recht. Ob ich den Verlust der 3 f: am louis d’or
in die Ausgaab, oder in die Einnahme Rechne. Genug, sie sehen hieraus, daß alles
Theurer ist. [Briefe, i:115]

The Louis d’or has 24 livres; consequently 4 Cronthaler [= 4 Laubthaler, both are
German terms for a French écu], then each Laubthaler is worth 6 livres. A livre
has 20 sols [sous]. A sol has 4 liards. If you now take liards to be pfennigs, then a sol
is a kreuzer, consequently the livre is 20 kr, a Kronthaler 2 fl, the Louis d’or 8 fl. There
are no coins besides these, other than the six-liard piece, which by my reckoning
is 6 pfennig, and the 2 sol piece, or 2 kreuzer, the twelve sol piece, or 12 kr, the
twenty-four sols or 24 piece. Now you know every sort of money, for there aren’t
any others in France. I’m fully aware that a Louis d’or is worth more than 8 fl etc.,
but I manage better with this calculation, whether I figure the loss of 3 fl per Louis
d’or in the expenses or the income. Enough on this, as you can see that everything
is very expensive.

So Leopold acknowledges that his rule of thumb is inaccurate; his implication, when read in the context of the letter as a whole, seems to be that prices in Paris are so high that his rule of thumb is a more reliable practical guide to purchasing power than the official exchange rates. In spite of his acknowledgement of its inaccuracy, his conversion of 1 Louis d’or = 8 fl is used in the commentaries in Briefe to Leopold’s letters from this time.

In any case, the reported value of the gold snuff-box allegedly given to Wolfgang by Madame Victoire de France was probably only hearsay, and the gift would not (probably to Leopold’s annoyance) have been directly negotiable as currency. With those caveats in mind, 80 Louis d’or would have been equivalent to 880 fl (using the 11 fl exchange rate) or 640 fl (using Leopold’s rule of thumb). A large difference, but it would have been a very valuable gift in either case.

The reports in the Berlinische Nachrichten and Wienerisches Diarium give Wolfgang’s age as seven, as do the original title pages for op. 1 and op. 2. Wolfgang had, in fact, turned eight on 27 Jan 1764. The widely circulated report on the Mozart children in L’Avantcoureur on 5 Mar 1764 more accurately states that Wolfgang had “completed his seventh year” on his most recent birthday.