Hi Alan
From what I can see, you have an early No. 10H. The early Stuart engines (up to the 1920's) had single sided crossheads as per the current No. 1 engine. I have seen examples of single sided crosshead No.10Vs, No. 10Hs and I myself own a single sided crosshead No 7. In the late twenties / eary thirties the No. 10Vs and No. 10Hs changed to trunk guide crossheads as per the present versions. What was originally called the No 7 changed to the trunk guide crosshead 7a; I guess they didn't change the No 10 series to 'a' versions as these already had a letter suffix.
With regards to your boiler, I have never seen a No.50 before. The end plates of this boiler have been hacked about a bit; the hinged door replaces two dummy doors that were cast into the endplate, you can see the remains of the cast doors at either side of the new one. If you look at the end of either a 500, 501 or 504 boiler you will see what I mean. I am guessing the boiler has three tubes underneath. I think that this might be a 500 Babcock boiler and someone has possible filed away the last zero. Why they have done this I would not like to surmise. The back head of the boiler has bee bodged about quite a lot as well, the solder is much messier than would have been original. The good news is that all four mounting lugs are intact, these were somewhat fragile and frequently snapped off at the slightest hint of over tightening.
The dynamo is a genuine Stuart item, no longer made and quite expensive to buy, if you can find one. These regularly make £100+ on ebay. Unfortunately, all the original Start green paint has been removed and it has been polished. Unfortunately this over enthusuastic 'restoration' will have reduced it's value considerably.
Hope this information helps, regards
NickM
Edited By Nick Moody on 10/09/2013 14:59:41