The turret is an early model and had 3 track holders on the right side, giving a build date of mid- to late April 1943. Most of May 1943's deliveries went to 502, but a few went to GD and SS regiments.
There seems to be a dark-outlined turret number, second digit '3', first digit possibly '1'. The three is flat- topped rather than rounded. This combination of features we associate with 501 and 3SS. The digits look relatively thin which is more suggestive of Totenkopf than 501, though the flat top of the '3' is longer than we would expect for either unit. We do not know of 501 on the eastern front receiving any early build models.
There is a possibility that this Tiger was rebuilt and issued to a new unit. From photographic evidence we most associate these with 501 and 502. We would expect a rebuild to have Zimmerit but cannot see it here (possibly because of photo quality). The removal of the smoke discharger brackets looks to have been relatively crude and is more suggestive of work done in the field than in a factory.
Don't think we can be sure at this stage, but if it's a rebuild its probably 501; if it's still with its original unit, 3SS is most likely, though the first digit would be '9' rather than '1'.