675fps is about right for the Sheriden. I don’t recall the pellet weight off hand but it was heavy for it’s caliber which really makes all the difference in penetration.
For that matter 675fps is about the velocity of the .38 S&W cartridge. It would penetrate a lot more than one board.
I have 5 .177 springers right now which are rated at 1000fps. I don’t have a chrony but have read enough reports by owners who do that most of them are no where near 1000fps except with the very lightest of regular pellets. Even then most are well under 1000fps. I do have one, a Turkish made one which I think is a bit hotter than the others.
I have actually owned and shot a Sheriden for many years. They really are powerful.