One of the trickiest things with stationery is the most frequent motives... Views from scenic places
I´ll try to make a guide here for 3 different areas, all for prestamped envelopes with 1st Coat of Arms type 1957 - 65.
1. Tourism / Views from Romania
2. Views from Bucharest
3. Views from the Carpathic Mountains / Winter sport
I hope I get it right

Tourism / Views from Romania

1957
U27
7 lines, 5 lines with receiver, line + 2 lines with sender
Price vertical
No perf
short rays of sun
55B (1L)red 14 images  of Romania + 2 of tractors + 1 of electricity mast

View from Bucegi, Peisaj din tara, Peisaj din munte, View from Tusnad
Casa de odinha (Rest home), Casa de odhina 2, Casa de odhina 3
1958
U35
7 lines
Oficiul Postal in box
Text on reverse: Important!
No money or valuables etc..
ditto 55B (1L) red
8 images w tourist views

View from Tusnad
Tractor, Electicity, folk costumes (as U28), ship model build
1958
U41
 7 lines
Oficiul Postal in box
No text on reverse side
ditto 55B (1L) red
4 images
1958
U52
unknown as yet ditto 55B (1L) red
4 images
1958
unrecorded
Destinatar, 7 lines
with Etaj___Apart__
Oficiul Postal in box

+ price vertical
ditto 55B (1L) blue
 4 images


Bran Castle
1958
U57
Destinatar, 5 lines
Oficiul Postal in box
If box is brighter it has text vertical at left:
Photo C. Savulescu
If box is same colour as
letter then no text

perf
dark background
55B (1L)black 12 images - seems each image can be of each type

Lake Herastrau sailing, Slanic Prahova 1, Liberty park - swans, Dimbovicioarei bridge
Javelin statue, Lake Amara, Lake Herastrau - birches, , Slanic Prahova 2, Danube delta
Sunset at Danube   (that´s 10/12)
1958 5 lines
white paper
ditto 55B blue
55B black
4 images

Lake Amara, Slanic Prahova
1958 Unrecorded
5 lines + text about price vertical
ditto 55B blue

Liberty Park Bucharest,
1958 Destinatar + 4 dotted lines +

 box w Oficiul Postal

perf
dark background
55B ultramarine
55B red orange

Cismigiu, Ateneul, Arad, Poiana republicii, Predeal, Sinaia 1, Sinaia 2
1959
U83
4 equally long lines No perf
short rays of sun
55B blue 5 images

Ateneul, Cismigiu
1959/60
Unrecorded
3 equally long dotted lines
1 shorter, thicker
Perf 55B red
55B blue

Babele (rocks), Busteni
1959
U84
Destinatar + 5 lines
+ price vertical
No perf
short rays of sun
55B red orange  
23 August stadium,
1961
U149
Ultimul oficiu postal
Type 1: 7 short lines
Type 2: 4 short lines, 2 long

(type 2 might belong elsewhere...)

ditto 55B blue 8 images

Type 1: Tusnad (shown), Poiana Brasov
1962
U163-4
Ultimu oficiul postal
4 lines
ditto 55B blue
55B black
12 images

Paltinis,
1963 Destinatar 4 lines
+ box w oficiul postal
ditto 55B blue
55B bluegrey
12 images

Ateneul,  Cismigiu, Herastrau Park, Pillar Bistrita
1965 Destinatar 6 lines
+ box Oficiul postal
ditto 55B greygreen 12 images

Spre Predeal,

 

Views from Bucharest

1959
U82
2 long lines +
i divided
No perf, large,
55B (1L) ultramarine 5 images

Boulevard Magheru, 23 August stadium,
Atheneum, Opera, Press house) Athenee palace (looks a bit different)
1960 I´ve placed 2 designs here, for lack of better knowledge:
Design 1:
2 long lines, 2 half limes, the right one thicker
Design 2:
3 long lines + a smaller thicker line
(placed middle or right..)
no perf, small
striped background
55B (1L) red
55B (1L) violet
11 images

Design 1: Athenee palace,
Design 2: Stavropolous boulevard, Michael the Great statue, President Council, University Square
1964   ditto 55B (75B)olive
55B (1L) blue
Olive - 5 images Blue - 6 images in 2 variations


Views from Carpathic Mountains / Winter Tourism

1959 Winter
U88-90
3 long, 1 short line no perf 55B (1L) red
55B (1L) ultramarine
55B (1L) violet
15 images

Skiing (shown), Christmas trees in Bucharest, Liberty Park, Winter landscape,
Winter in Cismigiu, Liberty Park 2, Predeal - bobs, )
1959 Winter
U91-92
3 dotted lines +
1 accented line 

Seems to be 2 versions:
1. 2 lines + 2 1/2 lines
2. 3 lines + accented line
perf 55B (1L) light blue
55B (1L) red
6 images

Type 1: Bucegi,
Type 2: Predeal, Bucegi massive
1961 Winter
U148
4 short lines
2 long

starts w Ultimul oficiul postal 
no perf 55B (1L)violet
55B blue (unrecorded)
8 images

Looking at cottage, Skis on shoulder, Hands in pocket, Birds in tree
1961 Carpath
U150-153
Type 1: 7 lines equally long 
Type 2: 5 short, 2 long

starts w Ultimul oficiul postal 
no perf 55B (1L) blue
55B (1L) carmine
55B (1L) dark brown
55B (1L) dark violet
14 images

Mt Fagaras: Skiing (shown), Skis against wall, Winter view
Bucegi: On top (shown), Cabana Girbova, Cabana Diham, Winter, pe valea lalomitei

Mount Bucsoi
1964 Winter
U208
6 lines + box
Starts w Destinatar 
no perf 55B (1L) blue 4 images
1964 Carpath
U215-217
same as U208  no perf 55B (1L) brown lilac
55B (1L) black
55B (1L) greygreen
11 images

Hotel Turistic Poiana Brasov, Cabana Diham,
Cabana Piatra Arsa