The theft happened at a compound near to Worksop station on Saturday 11 November. During the mid-afternoon, at approximately 4.15pm, a man approached a compound at Worksop station.
He then disconnected a large generator and towed it away using a white dropside truck which had false plates on. It is then believed the generator was taken to the Derby area.
Officers would be keen to speak with anyone who recognises the man in the images as they believe he might have important information.
If you know who he is, please contact BTP by sending a text to 61016 or by calling 0800 40 50 40 quoting reference 67 of 11/11/2017. Alternatively, pass information anonymously to Crimestoppers on 0800 555 111.