See What are differences between the Librem versions? as well as the whole thread.
Librem 15v4 (from the Wayback Machine)
Technical specs
| Operating system | PureOS |
|---|---|
| TPM | Included |
| Battery life | Roughly 6 to 9 hours |
| Processor | Core i7 7500U (Kabylake) |
| Display | 15.6″ matte 3840×2160 |
| Graphics | Intel HD Graphics 620 |
| Memory | Up to 32GB, DDR4 at 2133 MHz |
| Storage | Configurable |
| Chassis | Black anodized aluminium |
| Webcam | 720p 1.0 megapixel |
| Dimensions | 375×244×22mm |
| Weight | 1.8kg |
| Wireless | Atheros 802.11n w/ Two Antenna |
| Radio hardware killswitch | Yes |
| Mic and cam killswitches | Yes |
| Audio port | 1 headphone/line output jack |
| USB ports | 3 USB 3.0 Ports (1 type C, data transfer only), 2 USB 2.0 Ports |
| External monitor output | 1 HDMI Port (4K capable @30Hz max) |
| Card reader | Yes, 2-in-1 SD/MMC |
| Backlit keyboard | Yes |
| Touch interface | Elantech Multitouch Trackpad |
| Thermal design | Low noise fan |
The Wayback machine doesn’t have the same table for the 15v3 … but I think the 15v3 is the third column of this https://web.archive.org/web/20180905015205/https://puri.sm/products/
So the biggest differences are:
Core i7 6500U
Intel HD Graphics 520
Up to 16GB DDR4 at 2133 MHz
15.6" 1920×1080p matte display
Both of them had issues with the hinges/case breaking, but I think the 15v3 was worse.
To check for sure which you have, you can verify the CPU by looking at /proc/cpuinfo: cat /proc/cpuinfo | grep “model name”