The East of England Co-op store in Dedham suffered major structural damage when the raiders drove a Toyota Hilux into it during the early hours of 10 December 2017.
A spokesperson from Essex Police said that the suspects fled the scene in a second vehicle. No arrests have been made in connection with the crime.
Major damage was caused to a section of shop front dating from the 1950s. The timber-framed building was originally built in 1520 as a merchants' house.
The incident led the Co-op to commission archaeologists to examine the building and to carry out a dig beneath its floor.
They found a medieval hearth, which pre-dated the surviving buildings as well as the remains of an internal porch, a feature rarely found in England before the Elizabethan period.
Archaeologists also uncovered a two-handled tripod cauldron dating from the late 16th to early 18th century.
The cauldron was buried near the building's original entrances and may have been intended to prevent evil influences entering the house, Colchester Archaeological Trust said.
An architectural historian, who worked on the excavation, added that the building's timber joisting and beams were the finest that the group had ever seen.
“We are delighted with the evidence these reports have revealed about the rich history of this important part of the borough and the wealthy merchants who lived and traded there," Dr Jess Tipper, an archaeologist for Colchester Borough Council, said.
The shop was moved into a barn after the raid but will re-open at its high street site on Tuesday.
Its security has been boosted, with concealed steel now embedded into the shop front.
Additional reporting by agencies.
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