Majumdar, R.C. 1945. “Two Copper-Plates of Śaśāṅka from Midnapore.” Journal of the Royal Asiatic Society of Bengal, Letters 11 (1): 1–9.
I have checked the amazing Biodiversity Heritage Library (http://www.biodiversitylibrary.org), which has many volumes published by the (R)ASB available in digital form, but apparently not this one.
Thanks.