Here we include the continental imports that were in use after the departure of the Roman legions. The "Dark Ages" - cover the period after the Roman withdrawal in 409 AD through the 6th century to about 600 AD. Frankish coins played an increasingly important role as currency in England as the 6th century went on, and the earliest Anglo-Saxon gold tremisses (sometimes referred to as thrymsas) were struck to circulate alongside these Frankish issues: all of the forty gold tremisses found in the burial at 'mound one' at Sutton Hoo (deposited c. 630), for instance, were Frankish. The earliest coins struck in England can be roughly dated to around the year 600.
D.M. Metcalf, Tremisses and sceattas from the South Lincolnshire productive site BNJ 86 (2016), pp 96-117.
I. Stewart, ‘A solidus from Yorkshire’, 56 (1986), 182-83
Dhénin and P. Leclercq, ‘The coins of Quentovic from the Cuerdale hoard in the museum of Boulogne-sur-Mer’, 52 (1982), 104-07
Dolley and N. Shiel, ‘A Carolingian denarius with a Devonshire provenance’, 50 (1980), 7-11
J. P. Campbell, ‘A Merovingian copy of a tremissis of Justinian I found in Kent’, 44 (1974), 74-75
H. M. Dolley, ‘The authenticity of the Palatina obolus of Lothaire II found at Litton Cheney in Dorset’, 34 (1965), 167-68
H. M. Dolley and K. F. Morrison, ‘Finds of Carolingian coins from Great Britain and Ireland’, 32 (1963), 75-87
H. M. Dolley and D. M. Metcalf, ‘Two stray finds from St Albans of coins of Offa and of Charlemagne’, 28 (1955-57), 459-66