http://www.botanical-online.com/chaenomelesjaponica.htm the image I used for comparison. another: http://www.hort.uconn.edu/Plants/c/chaspe/chaspe1.html another: http://encyclopedia.laborlawtalk.com/wiki/images/thumb/c/c1/240px-Quince8317.JPG seems like there isnt a heck of a lot of difference in the flower from a visual standpoint. it is a bit difficult to guage size from these photos however.
C. japonica is the low growing orange one. "A small, spreading shrub with bright orange-flame flowers followed by rounded, yellow, fragrant fruits" (HILLIER MANUAL OF TREES & SHRUBS*). Posted photo looks quite like C. speciosa, "the well-known, early-flowering japonica [UK], a much-branched, spreading shrub of medium size. Seedling-raised plants may bear flowers of mixed colours, but predominantly red" (Same). *2002 Hillier Nurseries and David & Charles
Chaenomeles japonica "...Flowers orange red, scarlet or blood red on year old wood:..." Dirr's manual of woody landscape plants. otherwise the books agree in regards to plant habit and stature. Seems like it is a hard one to really peg down for sure. its a Flowerinf Quince, thats for sure, the variety may be in question.