3 points to distinguish between SMC and BMC manhole covers on the Chinese market.

No1. First, ask the supplier about the composition of the raw materials.
SMC: glass fiber (sheet molding compound), resin
BMC: glass fiber (bulk molding compound), resin, steel keel

No2. design pattern is not same
SMC: holes, no handles
BMS: with handle, no hole

No3. Look at the back of the product
SMC: Flat and smooth
DMC: Square lattice

And the most important point is that SMC is 2-3 times more expensive than BMC