A browse through currently available offerings might be a good start: **LINK**
https://uk.rs-online.com/web/c/power-supplies-transformers/transformers/variacs/?sra=p
Find something of similar weight and it will probably have a similar rating.
After that … run some load tests and see when it starts to get warm.
MichaelG.
.
Edit: Here is a Torovolt on ebay, for comparison
https://www.ebay.ie/itm/Variable-Transformer-240V-0-6A-Cressall-Torovolt-33Y-Variac-Unused-/192484445526
and a link to Cressall's web-site: https://www.cressall.com/about-us/
Edited By Michael Gilligan on 20/06/2018 14:20:37