The above is an official award. Conferred in recognition of achievement or performances of a degree equal to that for which an individual would be awarded the Medal of Honor or Distinguished Service Cross (DSC). The group (all four squadrons - 815th, 816th, 817th & 840th - included) received two awards: for the Memmingen Raid, 18 July 1944 and a raid on Berlin, 24 March 1945. Given his dates of service, your Uncle Harry could well have participated in both but the only way to determine for certain is to access records. Embossed certificates are similar to those which accompany awards of personal decorations (such as the one he received - or should have - with his Air Medal). These were produced after the war and usually issued only upon request.
As indicated, the "Lucky Bastard Certificate" you referred to is unofficial. These were locally-produced at private expense and "recognized" successful completion of a combat tour.