Invasion of Britain coinage issued during the 1st Tetrarchy

[Victor]

In A.D. 294, Constantius I began to prepare his forces for the invasion of Britain and subsequent defeat of the usurper Carausius. The coins below were struck for all members of the Tetrarchy--Diocletian, Maximianus, Constantius and Galerius. Initially, numismatists believed that these coins were minted in London, but the style is different and seems more like the Lyon mint. The coins were likely struck at an unknown continental mint (maybe Boulogne) staffed by Lyon mint workers.

[Gavin]

Victor, is there any clear or dispositive sign to ID these issues? I don’t suppose the absence of the mint mark is the only sign. Is it a combination of mint mark absence and an overall style that a numismatist simply develops an eye for over time? That’s a clunky sentence, but I think you understand my meeting.

[Victor]

The easiest way to tell the no mintmark invasion coinage apart from the no mintmark London coins is the obverse bust. Invasion coinage has a head only while the London coinage has a cuirassed bust, like the coin below.

[Gavin]

Thanks. That’s very helpful.

[Heliodromus]

I'm not sure how much consensus there is, but the latest discussion that I'm aware of (Drost, 2014) rehabilitates the Lyonese style "continental mint invasion coinage" as simply the first issue minted at Lyons itself. He presents a variety of evidence for this, including a die link from one of these unmarked marked coins to the Lyonese PLA issue.

 

There is also the unmarked London "intermediate group" immediately following the first "LON" coins, which RIC omits. I believe these were first written about by Mossop in 1958, then Basten in 1959 and later in NC 1971 where he illustrates the stylistic continuity from the LON coins through the intermediate group into the later class II group. There is also Stewartby's later NC 1998 paper discussing these.

So, from London in date order we have:

1) LON = Stewartby 1a         = CT 1.01 laureate
2) Stewartby intermediate Ib  = CT 1.02 laureate
3) Stewartby intermediate IIe = CT 1.03 LC (+ rarely LDC), cuirasse typically with >>> chevron decoratoin
3) RIC Class IIa, IIb         = CT 2.x
4) RIC Class III              = CT 3.x

Bastien - Some Comments on the Coinage of the London Mint, AD 297-313 (NC 1971)

Stewartby - Early Tetrarchic Coins of London from the Market Stainton Finds (NC 1998)

Drost - Les nummi sans marque de style lyonnais (Rev Num 2014)

Here's some examples:

Lyons first unmarked issue

 

London Ia

 

London intermediate Ib

 

London intermediate IIe

 

London IIa

 

[Victor]

thanks for the Drost info.