The 45 was made for the American market.

Back in the early 70s, Americans were getting into the “adult air gun” thing, focused on German and British springers.

The top rifles were the HW35, BSF55/65/70 and Diana 35. All around 9-12 ftlbs in .177”.

Then, in fairly short order, the FWB Sport turned up, making 13-14, and then independent testing suggested that (in the American preferred calibre of .177” - I think the difference is a fair bit less in .22”) was both less powerful than the others, and than Diana claimed. That kind of did for the 35 in America.

The 45 gave Diana something bigger, heavier, equally powerful and cheaper than the FWB. I think it sold OK in the US, but the FWB’s established place in the market, cachet, lightness, handling, etc, kept it in pole position until Beeman and Weihrauch came up with the HW80/R1. Similar size to the 45, but about an extra 50% muzzle energy.

Which makes none of us any wiser as to the “S” models. For me, the key point is that they were brought in across the 25/27/35. Hence my theory they were misguidedly 10M target-oriented.