That is a huge drop on his recent 60kg and 59kg handicaps, with the only other time he has carried 55kg in New Zealand being when fourth in March's Awapuni Gold Cup.
But back then there was a difference. Back then Eagle Mountain was still a stallion, which is how he ended up in New Zealand in the first place.
He arrived for stud duties two years ago after a glittering career.
Eagle Mountain was a world-class 3-year-old, finishing second to Authorized in the English Derby in 2007 before going on to run second in the Breeders Cup Turf the following season on his way to winning the Hong Kong Cup.
That all made Eagle Mountain a viable stud prospect for Brighthill Farm when he arrived in 2010.
But after being plagued with fertility issues that have left him with just a handful of foals, Eagle Mountain was put back in work.
He resumed his career in February and even for a horse used to the greatest tracks in the world it was a steep comeback, taking on Veyron and Lady Kipling at weight-for-age in the Haunui Farm Classic at Otaki.
While the opposition has been easier since, Eagle Mountain's finishing positions haven't improved.
Yet McKee hasn't lost confidence there is still traces of the old Eagle Mountain inside his old frame and says the once outstanding galloper gets his chance this week.
"I was really happy with his run last start. He made ground well late and he really needed the run.
"He has improved on that quite a bit but the key thing on Saturday is the weight. Carrying 55kg for him is a luxury and that means he should be competitive this week.
"So if we can't get something positive out of him on Saturday I'll be surprised, and to be honest more than a little disappointed."
Still, Eagle Mountain is going to need to turn up armed with more than a few glory days tales from four years ago on Saturday, as he meets Undisclosed, Viadana and Shuka, who impressed when runner-up in the Coupland's Mile last start.
While Saturday could be termed D-day for Eagle Mountain, McKee's stable star Mufhasa is ticking along nicely for Saturday week's Captain Cook Stakes at Trentham.
"He is all good so all we want down there is a good track," said McKee.
But the old warhorse was not among the markets for the glamour sprints of the summer when they were released yesterday.
"It is his last season in the bigtime and he won't be going near handicap races again. He can just stick to weight-for-age."
