With the fall of the reign of Isabel II of Spain, a revolutionary period started, where all the structures (politics, economic and social) were trying to be updated. Within this modernisation, the most important currency system reform was introduced, undertaken in the modern and contemporary ages: the Order of 19th October of 1868.
This order puts to an end, the anarquic period where issuings from early centuries and the modern issues and reforms done during the reign of Isabella II, coexisted. This reform adopted, the model of the Latin Union, based in the metric system created by Napoleon and implemented by France, Belgium, Italy and Greece. All the coins issued by these countries were minted under the same alloy, weight and nominal values, both fractions and higher follow the ratio 1, 2, 5 and 10 (francs, lira, drachmas, pesetas…). We can observe that the monetary unit of all these countries weighs 5 gm, with a silver alloy of 835 thousandth. This, marked a great advance in the commercial and economic relationships between the countries within the Union. This was the early European Economic Union. The meaning of this introduction is to explain the weight of 33,26 gm of this assay of 100 pesetas of gold from Amadeus I. Following the model stablished by the Latin Union, the weight of this coin should have been 32,5 gm, as can be observed in posterior coinings of this value (e.g. 100 pesetas from 1897 of Alphonsus XIII). Starting from the base that 20 gold francs (the same for 20 gold pesetas, 20 gold liras, 20 drachmas, …etc.) weight 6,45 gm, a simple multiplication by 5 gives us the weight of the 100 pesetas.
So what´s the reason for this difference?
Goverments weren´t interested on putting more gold in a piece with the same interest rate as the rest of the coins from the Union that were equivalent. A possible explanation would reside in the short time the reform was ongoing and the tumultuous period of time when this coining was done. If we observe the average weight of 100reales/10 escudos from the previous era, this was between 8,37-8,38gm. Lets notice that 4 reales were 1 peseta (see issuings of 1 peseta from 1836 and 1837), for instance, in a theorical equivalence, 100 reales equals 25 pesetas*. If we multiply the weight of 100 reales by 4, we obtain a theoretic weight of 33,47-33,50*gm; a much closer weight to this numsmatic assay´s weight. This would imply that, inside the mint, the system of weights introduced by the reforms, wasn´t any clear, considering that by the same time 10 escudos with the name of Isabella II were minted with the weights of the previous reign.
As seen before, the possible following issuings of 100 pesetas from Amadeus I would have been adjusted to these weights from the monetary system of the Order of 19th October 1868. Not so the issue done as an assay (royal Decrete of 15th March of 1871 and 22nd Agost of 1871).
*This equivalency was observed, at a popular lever and tolerated by the different governments, from the Provisional Goverment until Alphonsus XIII. This “equivalency”, allowed the Public Tax Office, to obtain 0,2gm aproximately for piece.
** Strangely enough, the difference between the theoretical weight of the 100 pesetas assay, by the isabelline model, and the real weight is very similar to the previouos note.
Bibliography “LA PESETA” J.M. Aledón. Certificado de Autenticidad de Gabinete Numismático Calicó 5/02/1985.