Hi! This quarter has a few places that look like possible doubling. First is on the front, on the D of "God". It looks like some kind of doubling over the top right corner? Then on the last few letters of Liberty, they look thicker than usual and maybe slightly raised; not sure if that would be an error or not. And finally on the back, in the word Quarter; looks like slight doubling on top of the middle R and T, and possible in the bottom line of the E. I hope the picture's good enough, that's about as clear as I could get.
Hello! The D in "God" looks to be post mint damage ( PMD) or Machine Doubling which would not add any collector value. I am not seeing any extra thickness in LIBERTY. For the reverse, I am not seeing any doubling either. Your pictures are nice!
I just want to say keep up the good work - looking for varieties and errors can be rewarding and fun! Some resources I use to check for listed varieties are Wexler's die varieties (http://doubleddie.com) and Variety Vista (http://www.varietyvista.com/). They have great pictures for reference when looking for varieties! Happy collecting :)