So, others too have blue seals on their 2018 models.My D48 was bought new in Dec. 2020 by the original owner, who never used it. Since the receiver is dated to 2018, that's a pretty long gap, as far as retail environment is concerned. One possibility is that Diana used receivers made in 2018 to build 48/52's in 2019, when the new seal material was adopted. That would make the date on the guns false, though.My 48 runs at 28 J / 20.6 fpe now. I want to tune it to make 32 J / 23.5 fpe. At any rate, it's in the max power range of Hector's, and with the blue breech seal, the 1.75" gap should be a-ok as is.