As rightly pointed by “Peter” in comments, evidences now suggest Lumia 635 and not Lumia 735 heading to Sprint. As you can read below, It has passed Bluetooth certification as Lumia 635 and now the battery listed in FCC certification is BL-5H, which is used in Lumia 635. Even the charger in FCC listing is AC-20U, which belongs to Lumia 635. Lumia 735 uses BV-T5A battery with charger AC-20E.
So, now it seems the Lumia 735 Antenna dimensions may have been copied by mistake to RM-1078 certification.
A new Lumia variant RM-1078 has been seen at FCC and first reported by PhoneArena. This phone supports all Sprint LTE bands and is a GSM / CDMA phone too. Now the size specs of 134.7 X 68.5 confirm it to be another Lumia 735 variant. The Sprint logo can also be seen on the above label, though obfuscated. Check the crop below,
Surprisingly this devices has passed Bluetooth certification as Nokia Lumia 635, but based on our experience, we can tell that it should be a Lumia 735 variant only, as it has been clubbed with all other Lumia 730 / 735 variants (standard practice)