Octavian (aka Augustus) conquered, or annexed, Egypt when Antony and Cleopatra committed suicide after the battle at Actium. Between 30 BC and AD 20/1 silver coins were not minted in Egypt and old Ptolemaic silver continued to circulate. Tiberius in his seventh regnal year (20/1) introduced a billion tetradrachm that was lower in silver content than Ptolemaic tetradrachms (25% vs. 33%), and which despite its heavier weight had roughly the same amount of silver as a Roman denarius.
Although these coins are known as "Alexandrian Tetradrachms", produced in Alexandria, they were not a civic coinage for Alexandria and circulated widely in Egypt and were not used outside of the province. Butcher & Ponting in their 2015 book on "Metallurgy of Roman Silver Coinage", Ch. 20, found hints, with a small sample size, of recycling of Roman denarii or silver from the same source used to mint Alexandrian tetradrachms - element signatures similar to Lugdunum imperial denarii. They also show that the Alexandrian tetradrachms were roughly aligned with silver content of neighboring coinages from Tiberius to Trajan. I am hoping that their next book provides some metallurgical insight into these two coins (Hadrian & Antoninus Pius). Note: a review of the Butcher & Ponting book here by William E. Metcalf. Although the printed edition carries a daunting price there is a ~$47 eBook option.
Nero issued large numbers of these, but never visited Egypt. Hadrian visited nearly every province of Rome including Egypt in AD 130 and where Antinous died and was deified as Osiris-Antinous. Antoninus Pius in contrast to his adoptive father, never visited Egypt, and uniquely didn't leave Italy during the 23 years of his reign.
I like the style of these coins, and the scale - especially the Nilus reverse on the Hadrian and the obverse portrait on the Antoninus.
Egypt, Alexandria, Hadrian, AD 117-138, dated RY 19=AD 134/135, Billon-Tetradrachm
Size: 23-24mm, 12.42g
Obv: AVΤ ΚΑΙС ΤΡΑΙΑΝ ΑΔΡΙΑΝΟС СEΒ. laureate head left
Rev: L ЄNNЄAK Δ, bust of Nilus right, wearing taenia and with slight drapery and cornucopia over shoulder
Ref:RPC III 5941; Dattari (Savio) 7450-51
Egypt, Alexandria, Antoninus Pius, AD 138-161, dated RY 3=AD 139/140, Billon-Tetradrachm
Size: 22-24mm, 13.06g
Obv: ΑVΤ Κ Τ ΑΙΛ ΑΔΡ ΑΝΤⲰΝΙΝΟϹ; bare head of Antoninus Pius, right
Rev: Eirene standing left, holding two grain ears in right hand and and caduceus in left arm, L TPI TOV around (regnal year 3),
Ref: Dattari (Savio) 2216; Köln 1320.