The filiation system of US army units is a bit intricate and it is the kind of topic where everyone can be right, depending of the period refered to.
It is true that if one visits the Institute of Heraldry
http://www.tioh.hqda.pentagon.mil/tioh.htm
and then goes to Engineer DIs identification page, then one finds a 27 th Engineers Bn
whose motto is "Omnes res bene facere"
http://www.tioh.hqda.pentagon.mil/Eng/2 ... talion.htm
But, on the other side, the mysterious DI is exactly the same as the one worn by 1 Engineers Bn, except that the colours are reverted (red instead of silver, silver instead of red; black instead of silver, silver instead of black) and there is a scroll with the motto : "Nunquam otiosi".
Before submitting my advice, I have consulted the "Engineers Catalogue" of the American Society of Military Insigna Collector, March 1967 ed. with sketches and descriptions by James A. Sawicki; the mysterious badge is identified p. 16, drawing 27A, fully in line with the picture submitted by our friend from Spain, as 27 Engineer BN.
Two other 27 Engineer BN DIs are depicted here, one unknown to me and belonging to the 27 ENGR Combat BN, and an other which is the same as the one given in the identification page of the Institute of Heraldry.
So: either J.A. Sawicki was completely mistaken (which I think hard to believe), or he refers to an older DI of the 27 Engineer BN. My considered opinion is that people from the 27 Engineer BN designed a DI (maybe in the interwar period) which was judged too similar to the 1 Engineer BN DI and took the opportunity of a amalgamation - there must be an american word for this, I do not know it, sorry - of some sort to design a new DI.