The Marlin M1 gear is expected to sport a 5.5-inch screen with a 1440 x 2560 resolution, a Snapdragon 820 chipset under the hood, 4 GB of RAM, and a 12MP/8MP camera combo - all the makings of a decent 2016 flagship. The S1 is likely to sport very similar specs, save for a shorter, 5"-5.2" screen diagonal, and a smaller battery capacity.
Long story short, the build.prop file you see below confirms at least a few of the S1 details that we've encountered so far. First off, the handset will seemingly land with a Snapdragon 820 processor indeed, as the "ARM64-V8a" and "msm8996" entries in the string indicate. The listed LCD screen density value of 420, however, hints that the HTC S1 might come with a ~5.2" 1080p display, instead of the Quad HD panel on the Marlin. Not that we are complaining, as 1920x1080 is a perfectly valid resolution for such a screen size, and will be gentler on the battery.
Last but not least, the Google Nexus Sailfish aka HTC S1 could be equipped with biometric security, as expected, as there are numerous finger- or thumbprint references in the string below, it's just going to be on the back, rumors tip, instead of at the front like on the HTC 10. Can you grasp anything more from the build.prop below?