After remaining closed for months under lockdown, the museum on Southgate opened for the two Heritage Open Days weekends this month.
Having quarantined the museum for three days after having visitors, chairman Mark Bamford popped in to tidy up and collect the post.
He said: “Amongst the post was an envelope with the words saying ‘anonymous donation museum’. I opened it when I got home while chatting to my wife, but stopped when I saw it contained £1,000 in old style £20 notes.”
Staggered by the generosity he said: “We have no idea who gave it to us, but I do not wish to track down someone if they want to remain anonymous. I would like to give out big, heartfelt thanks from the museum.”
Mr Bamford said it would help the voluntary organisation put on new exhibitions and offset running costs. He said: “We are only opening one day a week at the moment which is significantly reducing the amount we get in donations, so it has come at an opportune time.”
The museum did benefit from a £10,000 government grant passed on by North Kesteven District Council to help museums survive the pandemic.