I have 2 -1911's that I built using new Essex receivers and National Match parts. I have never seen a 1911 Essex. Only custom built 1911s with Essex receivers. (Ser#'s :724XX & 742XX)
I suspect yours was assembled from Remington Parts and a Essex receiver.
I have heard talk that the Essex receiver is poorly constructed and unreliable, but I have fired in excess of 3500 rounds from the 2 that I own over the last 10 years, without any problems.