The following photo shows both 1838 obverses side by side. The first has "Liberty" in raised letters which I believe represents the "Curved Date" variety and the second has "Liberty" incused which represents the "Straight Date".
Click on the thumbnail image for an enlargement.
Besides the difference in the word Liberty, the raised shield lines appear to be broader on the obverse with Libery raised.
The raised Liberty obverse die is known only on original issues including J76B-J76C/P89A-P89B, J79/P89, J82/P90, and J83/P91. No restrikes are known from this obverse die.
The incused Liberty die's earliest use for pattern coinage was on J79A/P86. These have been linked to 1843 where examples were struck for Matthew Stickney. All other usage of this obverse die were for restrikes made in the late 1860s to early 1870s including J76-J78/P82-P85 and J80-J81/P87-P88.
Photos used are courtesy of the National Numismatic Collection of the Smithsonian Institution.