Nottinghamshire and Derbyshire Tramways
Summary
There is some evidence to suggest that staff initially wore informal attire, however, given that the system was opened in sections, with many proving runs undertaken, it may be that the early photographic record shows these unofficial early operations as opposed to revenue-earning services.
Uniforms took the form of double-breasted, 'lancer-style' tunics with two rows of five buttons (narrowing from top to bottom) and upright collars; the latter appear initially not to have carried any insignia, though in later years they certainly carried 'N&DT' metal initials. The uniforms were of blue serge and the buttons appear to have been plain with a rim; there is anecdotal evidence that they were nickel, though this is based on memory of the last years of operation, so is potentially unreliable. Caps were in a military style with a tensioned crown (top) and carried standard, 'off-the-shelf', script-lettering grade badges - either Motorman or Conductor - presumably nickel to match the buttons. One photo exists which shows a motorman wearing an underlined script-lettering grade badge, suggesting that uniform policy was somewhat lacks. In the last few years of operation, motormen often wore 'Driver' cap badges, probably reflecting a general decision across the company, given its expanding bus operations.
A small number of staff in the 1913 depot photo below are wearing single-breasted jackets with lapels; these do not appear to be grade-specific, so it may simply be that the 'lancer-style' tunics were in short supply. Later on, probably shortly after the Great War, a switch seems to have been made - for conductors only - to single-breasted jackets with five buttons, two breast pockets; upright collars and epaulettes; the collars probably carried system initials, though the photographic evidence is hardly conclusive.
Tramcar crews were also issued with heavy-duty, double-breasted greatcoats with two rows of five buttons, high fold-over collars and epaulettes with button fastenings; the latter carried system initials - 'N&DT' - at the shoulder end, probably in nickel letters. Several photographs exist of motormen in oil skins, heavy aprons and leather mitts, hinting at the hardships to be endured in driving open-platform trams across country in adverse weather conditions.
Inspectors were issued with single-breasted jackets with hidden buttons (or an hook and eye affair) and upright collars; the jackets were edged in a finer material than the main jacket, and the collars almost certainly bore Inspector in embroidered script-lettering. Headgear was identical to that issued to tramcar staff, but with the grade - Inspector - in embroidered script-lettering on a hat band.
In common with the vast majority of UK tramway systems, the N&DT employed women in significant numbers during the Great War, to replace male staff lost to the armed services. These ladies were employed as conductresses, and were issued with tailored, single-breasted jackets with lapels and epaulettes, along with a long, matching skirt. The majority of photos however, show these ladies wearing heavy-duty, double-breasted greatcoats, which appear to have been identical in style to those issued to male employees. Caps were baggy with a glossy peak, and carried a standard grade badge - Conductor - though regimental sweetheart badges were frequently worn instead (also the case for male staff at this time).
For a detailed photographic history of the tramway, see 'Nottinghamshire and Derbyshire Tramway, including the Matlock Cable Tramway' by Barry M Marsden; Middleton Press (2005).
Images
Motormen and conductors
Staff photo taken in front of the depot at Langley Mill - undated, but almost certainly taken around the time of opening, i.e. summer 1913. With thanks to Heanor and District Local History Society (see link).
A blow-up of the above photo showing a group of motormen and conductors. Whilst the majority are wearing 'lancer-style' tunics, a small number are wearing single-breasted jackets with lapels.
Script-lettering cap badges of the type worn by Nottinghamshire and Derbyshire Tramways Company staff - nickel. It is currently unknown whether the N&DTCo issued these grade badges in brass or nickel, though there is some anecdotal evidence to suggest that it was the latter. Author's Colllection.
Conductor and motorman pose with a brand-new, top-covered Tramcar No 22 at Langley Mill depot in 1913. Photo courtesy of the Tramways and Light Railway Society, with thanks to David Voice.
A blow-up of the above photo showing the conductor and motorman, both of whom are wearing 'lancer-style' tunics with plain collars, i.e. devoid of insignia.
Tramcar No 1 waits at Ripley with a short working to Heanor - photo undated, but certainly taken during the Great War. Photo and background information courtesy of the Barry Marsden Collection.
A blow-up of the above photo showing the motorman, who is, somewhat unusually for a UK tramway system, wearing an underlined script-lettering grade badge rather than the almost ubiquitous non-underlined variety. The only badges on his heavy-duty greatcoat are on the epaulettes, which from other photos are 'N&DT' initials.
Underlined script-lettering grade badge - 'Motorman' - nickel. Author's Collection.
A rather tatty-looking Tramcar No 13 pictured in Station Road - photo undated, but certainly taken during the Great War. Photo and background information courtesy of the Barry Marsden Collection.
A blow-up of the above photo showing the fresh-faced motorman, who appears to be wearing some kind of cavalry cap badge (possibly homemade), along with what is almost certainly a curved military shoulder badge of some kind, perhaps 'FORESTERS', one of the local regiments. His robust leather mitts were a necessity given the N&DT's 13-miles of largely cross-country running.
Conductress, motorman and inspector with a very neglected looking Tramcar No 2 - photo undated, but certainly taken during the Great War or shortly afterwards. The 'N D T' collar initials can just about be made out.
Inspector, motorman and conductor with Tramcar No 4, possibly at Langley Mill. The photo is undated, but was probably taken around the time of the Great War.
A blow-up of the above photo showing the conductor. His collar initials appear to be 'C1'.
The motorman of Tramcar No 11 stands with his charge at the Ripley terminus in the last year of operation, 1932. Photo by M J O'Connor, courtesy of the National Tramway Museum. 
A blow-up of the above photo showing the motorman in full-length leather apron, mitts and upturned greatcoat collar, clearly indicating that working the N&DT with open platform vehicles in adverse weather conditions was not to be taken lightly. His cap bears a Driver grade badge rather than the Motorman type used earlier. Photo by M J O'Connor, courtesy of the National Tramway Museum. 
Script-lettering Driver cap badge - nickel. These badges appear to have replaced their Motorman counterparts late in the system's life, possibly reflecting the company's increasing expansion into bus operation. Author's Collection.
Senior staff
A blow-up of the depot photo above showing one of the inspectors.
A blow-up of the Great War era photo of Tramcar No 4 above, showing the inspector.
An inspector standing in front of Tramcar No 22 - photo undated, but possibly taken shortly after the Great War.
Female staff
Great War conductress Annie Bronson. The script-lettering cap badge and 'N&DT' epaulette initials are easily made out. The button is possibly plain with a rim. Photo and background information courtesy of the Barry Marsden Collection.
A blow-up of the photograph above of Tramcar No 13 showing the conductress. The greatcoat appears to be devoid of insignia, whilst the cap badge is once again military, possibly Royal Artillery.
A blow-up of the photograph above of Tramcar No 1 showing the conductress. She is wearing metal 'N&DT' system initials on her cap, presumably those which were normally worn on the epaulettes.