The 2nd contract included series AR - HR, 8 series of 25,000 each for a total of 200,000. The third was series OR, PR, RR, SR, TR, UR, XR, & YR, also 8 series of 25,000 each totaling 200.000. The Romanians picked the letters; no explanation known why some letters were skipped.
As for the vz.24JC mystery, I have checked into the older sources. Ottakar Franek's book does not sound well for your theory. He also mentions that the rifles were intended for the Brazilian plot from the beginning. He writes of the cover as just "China". The Brazilians paid an advance on the guns; so some were very likely shipped in time for the fighting in the revolution. He says the origin of the weapons was an open secret in Brazil. One rebel is quoted to the effect that ZB shouldn't worry about being paid because once they win, the Brazilian government will pay. This book is focused on the management and rarely gives specific models and characteristics of weapons involved. There was a big flap when the arrangement with the Brazilian rebels was accidentally discovered, and Franek wrote about 2 pages covering it. The flap is probably because many officials normally in the know were not informed due to secrecy. There was an investigation. In the end, incriminating documents disappeared, everybody denied sending weapons to Brazil, and the military warehouse installation denied taking anything out for export. In the mean time, ZB was busy producing 15,000 vz.24's to replace something from the warehouse. Not just ZB but Skoda cannons, gas masks, and 9 million rounds of ammo were involved. The investigation ruled there was no Brazilian deal, but the matter had to be strictly kept from the public. A classic cover-up?
Miroslav Ĺ ada only wrote 2 sentences about these rifles, which say that Brazil received rifles with intended origin "South China" (his quotes) which were 7mm caliber, with curved bolt, lighter stock and thinner barrel. This could very well be the origin of the theory that somebody in south China originally ordered them.
No, I don't really read Czech. I depend on the translation app. I can sing Czech hymns, say a few phrases.