code: private String getChainSpecification(List<Integer> modelNumbers, List<String> chainIds, int subunit) {
  		if (onTheFly) {
  			if (Collections.max(modelNumbers) > 1) {
  				return chainIds.get(subunit) + "&symop=" + (modelNumbers.get(subunit)+1);
  			} else {
  				// if there is only a single symop, Jmol does not accept the symop syntax
  				return chainIds.get(subunit);
  			}
  		} else {
  			return chainIds.get(subunit) + "/" + (modelNumbers.get(subunit)+1);
  		}
  	}
docs: --- private methods ---