The following information was provided by Mike Brodsky, University of Massachusetts Medical School.
P{arm-GFP.B} is a pCasper2 construct with 1.8 kb of regulatory sequences upstream of armadillo driving expression of EGFP.
P{arm-GFP.B}2 is an insertion into the CyO balancer. It expresses GFP ubiquitously in embryos and larvae.
Bloomington will use CyO, P{arm-GFP.B}2 as the short name of this balancer variant.
This balancer variant was mentioned briefly in Sullivan et al. (http://flybase.org/reports/FBrf0128659.htm) and it has been mentioned in passing in several subsequent papers.