The type of output should be labelled on the transformer if it is a free standing unit. Only if it is a integral part of an assembled unit could it be left un-labelled.
Transformers provide AC, if the item provides DC then it is a transformer AND rectifier or it is an electronic power supply unit.
Can you provide a photo of the old transformer where the label can be seen ?
24V ~ suggests AC
24V = suggests DC
Thanks for reply Bernard. Photos below. So with the "~" it looks like 24V AC output. Is this a standard convention?