Your piece—marked "J Steventon and Sons Ltd Burslem England" with a pattern number—is authentic Royal Venton Ware, produced c. 1890s–1930s in Burslem, Staffordshire (heart of The Potteries). Known for cream-colored "ivory" body and Art Nouveau floral transfers, it's a respected but not ultra-rare line.
Pre-WWI pieces (1890s–1914) command premiums. Pattern numbers help date: lower numbers = earlier. Limited runs (commemoratives, children's sets) scarcer.
Tea sets (especially complete) > single pieces. Unusual forms (chocolate pots, moustache cups, dresser sets) > standard plates/cups. Art Nouveau flowing florals > later geometric Deco patterns.
Original boxes, receipts, family history add modest premium.
Likely modest value unless rare pattern/pristine/complete set. But historically lovely—representing Staffordshire's golden age of transferware.