? on 25c Surcharge
Stanley Gibbons SGNC300a Surcharge (a similar type)
Yes, it's a communist issue for North China, listed in SG under "North China People's Post" in their North China listing.
I agree, SG NC300a looks right to me, with "a" as it's surcharged in grey rather than green.
The two characters in the lefthand column of the overprint read "one dollar" with the other characters as per SG type (NC74).