My first thought was that the first was for the Oxfordshire Light Infantry. Other ‘Light’ regiments had their initials suspended in the design. However it seems that most ‘Light’ regiments used the plain suspended bugle in the early 1880s. Of the Light regiments I can only find the Kings Shropshire Light Infantry in South Africa. They were there for about 8 months in 1881. The top button appears to have a crown over the bugle, but a better scan of this button might help.
I think you will also have to do a better scan of the bottom button in the second photograph. It does not appear to be for the RA or Royal Marines; nor the general service pattern, so a higher resolution scan may give the regiment. Again there could a suspended bugle present.
Ken