http://911research.wtc7.net/wtc/evidenc ... rames.html
Fact: these blueprints are only for the North Tower WTC1.
#1 observation: North is incorrectly annotated on the blueprints. The arrow is drawn to show the north face of the building pointing directly north. As shown in this analysis
http://forum.911movement.org/index.php? ... p=15328057
the north face of the North Tower was facing 29.5 degrees to the east.
No draftsman would make an error of this magnitude.
#2 observation: the blueprints are optically inverted ("negative") versions of original drawings. Blueprints from those days had a blue background and chalky-white foreground. The "blueprints" shown at this site have a white background with a black foreground - exactly the opposite of what would be expected for blueprints. These are more properly called drawings, not blueprints.
#3 observation: look at the "REVISIONS" tables in the bottom right corners of the drawings, to the left of the seal (bottom right area of the blueprint). On "1stFloorPlan", the tables look OK and hand-labelled, although two or three entries are empty.
Now, look at "1stFloorCorePlan". Look at the REVISIONS table, the entry 2-1-71 (as best as I can tell). Each revision consists of four columns - the first column is a hand-drawn triangular icon, the other three columns contain hand-lettered text - date, some sort of reference number, initials.
In the left-most column, there are four entries. In the third entry down, the initials (fourth column) look clearly out of character. The lettering in columns 2 and 3 is in keeping with the lettering throughout the REVISIONS table, but the initials in the third entry down look distinctly out of place.
Here is what a normal set of initials looks like:

Here is a set of very odd-looking initials (I call them the U.N. initials):

Furthermore, someone with the initials OBL made revisions to the blueprints

The UN intials are overly-mechanical looking, to my eye. In 1971, the personal computer had not yet been invented (the IMSAI Altair 8800 came out around 1975, and the IBM PC was released around 1981).
It could have been possible to reproduce the UN initials using a set square, but such a waste of time would probably have been frowned upon by management.
Below is a list of drawings which were initialed by UN and OBL, along with dates, as best as I could make out.
Initialed by UN:
1stFloorCorePlan - 2-1-71
2ndFloorCorePlan - 8-1-71
6thFloorPlan - 8-1-71
6thFloorCorePlan - 8-1-71
9thAnd10thFloorCorePlan - 8-16-71
11thTo16thFlCorePlan - 2-1-71
24thFloorCorePlan - 8-1-71
26thFloorCorePlan - 8-1-71
41stFloorCorePlan_LowerMechEquipRmLevel - 8-1-71
44thFloorPlan_SkyLobby - 2-1-71
44thFloorCorePlan_SkyLobby - 8-1-71, 8-1-71
50thTo54thFlCorePlan - 8-1-71
60thFloorCorePlan - 4-1-71
61stFloorCorePlan - 2-1-71
63rdFloorCorePlan - 2-1-71
66thFloorCorePlan - 8-1-71
67FloorCorePlan - 8-1-71
72ndFloorCorePlan - 8-1-71
StairSectionsStair2_3 - 8-1-71
77thFloorCorePlan - 8-1-71
78thFloorPlan_Skylobby - 8-1-71
78thFloorCorePlan_Skylobby - 8-1-71
83rdFloorPlan - <blank>
83rdFloorCorePlan - 8-1-71, <blank>
89thTo93rdFlCorePlan - 8-1-71
94thFloorCorePlane - 8-1-71
95thFloorCorePlan - 8-1-71
96thTo100thFloorPlan - 8-1-71
96thTo100thFlCorePlan - 8-1-71, 8-1-71
101stAnd102ndFloorPlan - 8-1-71
101stFloreCorePlan - 8-1-71, 8-1-71
102ndFloorCorePlan - 8-1-71, 8-1-71
103rdFloorPlan - 8-1-71
103rdFloorCorePlan - 8-1-71
104thFloorPlan - 8-1-71, 8-1-71
104thFloorCorePlan - 8-1-71
105thFloorPlan - 8-1-71, 8-1-71
105thFloorCorePlan - 8-1-71, 8-1-71, 8-1-71
106thFloorPlan - 8-1-71, 8-1-71
106thFloorCorePlan - 8-1-71, 8-1-71
107thFloorPlan_RestaurantLevel - 8-1-71, 8-1-71, 8-1-71
107thFloorCorePlan_RestaurantLevel - 8-1-71, 8-1-71
108thFloorPlan_LowerMechEquipLevel - 8-1-71, 8-1-71, 8-1-71
108thFloorCorePlan - 8-1-71, 8-1-71, 8-1-71
109thFloorPlan - 8-1-71, 8-1-71, 8-1-71
109thFloorCorePlan - 8-1-71, 8-1-71, 8-1-71, 8-1-71
110thFloorPlan - 8-1-71, 8-1-71
110thFloorUpperLevelPlan - 8-1-71
110thFloorCorePlan - 8-1-71, 8-1-71
BulkheadRoof_CopingPlan - 8-1-71
TowerSectionSectionA - 8-1-71, 8-1-71
TowerSectionSectionB - 8-1-71
TowerSectionSectionC - 8-1-71, 8-1-71
TowerSectionSectionD - 8-1-71
82ndFloorCorePlan - 8-1-71
ScheduleOfDrawings - 1-4-71
FinishSCheduleZone5_7 - 1-4-71, 8-1-71, 8-1-71
FinishScheduleZone1_2_3 - 8-1-71
DoorBuckDetailsAndDoorSchedules - VOID
SubLevel1FloorPlan - 8-1-71, 8-1-71
SubLevel1CorePlan - 8-1-71
ServiceLevelFloorPlan - 1-4-71
ServiceLevelCorePlan - 1-4-71
Initialed by OBL:
9thTo16thFloorPlan - 6-18-71
11thTo16thFlCorePlan - 6-18-71
24thFloorPlan - 6-18-71
24thFloorCorePlan - 18-1-71
27thTo31stFloorPlan - 8-18-71
27thTo31stFlCorePlan - 6-18-71
35thTo40thFloorPlan - 6-18-71
35thTo39thFlCorePlan - 6-18-71
41stFloorPlan_LowerMechEquipRmLevel - 6-18-71
41stFloorCorePlan_LowerMechEquipRmLevel - 6-18-71
42ndFloorPlan_UpperMechEquipRmLevel - 6-18-71
42ndCloorCorePlan_UpMechEquipRmLevel - 6-18-71
EscalatorSectionsEscalatorsA3A4A5A6 - 6-18-71
43FloorPlan_LowerEscalatorLevel - 6-18-71
44thFloorPlan_SkyLobby - 6-18-71, 6-18-71, <blank>
44thFloorCorePlan_SkyLobby - 6-18-71, 6-18-71
45thFloorPlan - 6-18-71, 6-18-71
45thFloorCorePlan - 6-18-71, 6-18-71
46thFloorPlan - 6-18-71
46thFloorCorePlan - 6-18-71
47thFloorPlan - 6-18-71
47thFloorCorePlan - 6-18-71
48thFloorPlan - 6-18-71
48thFloorCorePlan - 6-18-71
49thFloorPlan - 6-18-71, 6-18-71
49thFloorCorePlan - 6-18-71, 6-18-71
50thTo54thFloorPlan - 6-18-71, 6-18-71
50thTo54thFlCorePlan - 6-18-71, 6-18-71(?)
55thAnd56thFloorPlan - 6-18-71
55thFloorCorePlan - 6-18-71
56thFloorCorePlan - 6-18-71
57thAnd58thFloorPlan - 6-18-71
57thAnd58thFlCorePlan - 6-18-71
59thFloorPlan - 6-18-71
59thFloorCorePlan - 6-18-71
60thFloorPlan - 6-18-71
60thFloorCorePlan - 6-18-71
61stFloorPlan - 6-18-71
61stFloorCorePlan - 6-18-71
62nd63rdFloorPlan - 6-18-71
62ndFloorCorePlan - 6-18-71
63rdFloorCorePlan - 6-18-71, 6-18-71
64thFloorPlan - 6-18-71
64thFloorCorePlan - 6-18-71
65thFloorPlan - 6-18-71
65thFloorCorePlan - 6-18-71
66thFloorPlan - 6-18-71
66thFloorCorePlan - 6-18-71
67thFloorPlan - 6-18-71, 6-18-71
67FloorCorePlan - 6-18-71
68thFloorPlan - 6-18-71
68thFloorCorePlan 6-18-71
69thFloorPlan - 6-18-71
69thFloorCorePlan - 6-18-71
70thAnd71stFloorPlan - 6-18-71, 6-18-71
70thand71stFlCorePlan - 6-18-71, 6-18-71
72ndAnd74rdFloorPlan - 6-18-71
72ndFloorCorePlan - 6-18-71
73rdFloorCorePlan - 6-18-71
74thFloorPlan - 6-18-71, 6-18-71, 6-18-71
74thFloorCorePlan - 6-18-71, 6-18-71, 6-18-71?
110thFloorCorePlan - 6-18-71
FinishScheduleZone5_7 - 6-18-71
FinishScheduleZone1_2_3 - 6-18-71
DoorBuckDetailsAndDoorSchedules - 6-18-71