Mark,
On 15 Nov 44, 200 Armoured Delivery Regiment (British), sent a document to it’s subordinate units including ‘B’ Canadian Armoured Delivery Squadron, which detailed the current sighting devices for various equipment. The document shows British and American Periscopes, Telescopes, and Dial sights. There are multiple sections of the document, with the first sections being alphanumeric lists of the sights with the intended application, then there is a section which lists vehicles and details the applicable devices.
The cover page can be found here:
https://heritage.canadiana.ca/view/o...eel_t12746/774
If this document is correct, then it appears that M10 3” was issued with US telescope panoramic M12A4 “if fitted”, but it appears that there was no dial sight issued to M10 17-pr.