Hi Mike,
I have checked my past sales and find that I have owned 10 x 1858/6’s over the years. A long time ago I realised that, like some other overdate pennies in the YH series, it is often possible to identify an 1858/6 without being able to see the date. All of my 10 coins have had the same features on both obverse and reverse which indicates that this type is always struck from a single die pairing.
Having said the above, and also just checked ebay where I can see at least 2 of these, I don’t think it is as common as an 1858/2 or an 1858/3, and far less common than combined 1858/7 types.
For 1858 known varieties my ‘top of the head’ guess would be to place it roughly on a par with Bramah 26a No WW Missing Serifs, but definitely more common than the two ‘Large Rose’ types.
Hope this helps.
I really need to attempt some 1858 stats from my 5-year ebay study!
P.S. The Ingram coin shown above is the type described by Michael Gouby as 1858/2